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CHEMISTRY 

OF 

THE  FARM  AND  HOME 


BY 


WILLIAM  EDWARD  'NOTTINGHAM 

Assistant  Professor  of  Agricultural  Chemistry, 
University  of  Wisconsin 


AND 


JOSEPH  WAITE  INCE 

Assistant  Chemist,  North  Dakota  Experiment  Station 

Formerly  Professor  of  Agricultural  Chemistry, 

North  Dakota  Agricultural  College 


WEBB  PUBLISHING  CO. 

ST.  PAUL,  MINN. 

1916 


h/^ 


COPYRIGHT.   1916 

BY 

WEBB  PUBLISHING  COMPANY 

ALL  RIGHTS   RESERVED 
W-I 


PREFACE 

In  recent  years,  coincident  with  the  development  of 
secondary  schools  of  agriculture,  there  seems  to  have  de- 
veloped a  tendency  for  teachers  and  authors  to  dismember 
the  subject  of  chemistry.  To  a  greater  or  less  extent  this 
subject  has  been  appropriated  for  use  in  treating  such 
subjects  as  soils,  agronomy,  and  animal  and  dairy  hus- 
bandries. Such  treatment,  where  carried  to  an  excess, 
is  surely  to  be  deplored.  In  the  future,  as  in  the  past, 
the  basic  sciences,  chemistry  and  physics,  will  be  the  great 
sources  of  principles  which  guide  the  practice  of  agriculture. 
This  is  necessarily  the  case  on  account  of  the  leading  im- 
portance of  these  sciences  in  the  broader  field  of  physi- 
ology, a  subject  which  deals  with  the  mechanism  and  be- 
havior of  the  two  great  centers  of  interest  in  agricultural 
pursuits,  namely  the  plant  and  the  animal. 

Fortunately,  it  is  still  recognized  as  important  that, 
coincident  with  their  instruction  in  art  and  practice,  the 
students  of  agricultural  high  schools  and  secondary  schools 
of  agriculture  shall  be  instructed  in  the  elements  of  physics 
and  chemistry.  There  has  been,  also,  considerable  demand 
for  a  textbook  which  would  present  in  elementary  form  the 
whole  field  of  the  application  of  chemistry  to  agriculture. 
Too  many  of  even  college  texts  in  this  field  have  been  poorly 
balanced,  expanding  to  considerable  length  the  treatment 
of  some  subjects,  such  as  the  soil  or  the  plant,  and  yet  inad- 
equately covering  the  equally  important  subject  of  animal 
nutrition  and  its  related  topics.  An  elementary  textbook  in 
this  field  seems  likely  to  be  especially  important  for  students 
completing  their  education  in  the  high  school  or  secondary 

358835 


*       '^"  ^    ^  ^"         PREFACE 


school.  This  book  presents  sufficient  general  chemistry  in 
the  first  five  chapters  to  serve  as  a  foundation  for  the  study 
of  the  succeeding  chapters,  which  are  of  applied  character. 
The  authors  have  tried  to  make  the  text  both  informational 
and  stimulative  of  independent  thinking. 

The  summaries  of  the  chapters  will  be  helpful  for  review 
and  for  selecting  quiz  topics.  The  experiments  should  prove 
most  useful,  as  laboratory  methods  are  most  conducive  of 
abiding  knowledge.  The  material  allows  for  the  selection 
of  the  most  useful  experiments  under  varying  conditions. 
The  contents  of  the  appendix  will  be  of  further  assistance  to 
the  teacher. 

The  following  acknowledgments  should  be  made : 

For  information  concerning  feeding  stuffs,  The  Washburn- 
Crosby  Milling  Co.  For  illustrations,  Mrs.  F.  H.  King, 
DeLaval  Separator  Co.,  Institute  of  Animal  Nutrition,  The 
Utah  Experiment  Station,  The  North  Dakota  Experiment 
Station,  The  Wisconsin  Experiment  Station,  Swift  &  Co., 
Albert  Lea  Gas  Light  Co.,  The  Thermal  Syndicate,  Ltd., 
Morgan  Construction  Co.,  National  Carbon  Co.,  Booth 
Apparatus  Co.,  Wood's  Natural  Science  Establishment,  Bur- 
dett  Manufacturing  Co.,  The  German  Kali  Works,  Electro 
Bleaching  Gas  Co.,  Roessler  and  Hasslacher  Chemical  Co., 
Detroit  Heating  and  Lighting  Co.,  The  Emerson-Brant- 
ingham  Co.,  Miss  CM.  Eckhardt,  Universal  Portland  Ce- 
ment Co.,  and  Eimer  &  Amend. 

Other  contributors  are  acknowledged  in  the  text.     Ac- 
knowledgment is  also  made  to  Prof.  R.  W.  Thatcher,  of  the 
iJniversity  of  Minnesota,  for  a  critical  reading  of  the  text.  D. 
Appleton  &  Co.  for  figures  71,  72,  76  and  77. 
November,  1915.  The  Authors 


CONTENTS 


Chapter  Page 

I    General  Introduction 11 

Importance,  Elements,  Compounds,  Physics  and  Chem- 
istry Compared 

n    Water  and  Its  Constituent  Elements 22 

Distribution,  Kinds,  Circulation,  Purification,  Physical 
Properties,  Solution,  Chemical  Properties,  Usefulness, 
Climatic  Effects,  Relation  to  Water  in  Soil  and  to  Plant 
and  Animal  Life,  In  the  Arts,  Oxygen,  Ozone,  Hydrogen, 
Hydrogen  Peroxide,  Symbols,  Formulas,  Equations 

ni    The  Atmosphere  and  Its  Chief  Constituent,  Nitrogen 67 

Composition,  Nitrogen,  Acids,  Bases,  Salts,  Ammonia, 
Nitric  Acid 

IV    Some  Other  Non-Metals 89 

Chlorine,  Sulphur,  Phosphorus,  Carbon,  Simple  Organic 
Compounds,  Silicon. 

V    A  Few  Important  Metals 140 

Occurrence,  Extraction,  Sodium,  Potassium,  Calcium, 
Copper,  Magnesium,  Zinc,  Iron,  Aluminium 

VI    The  Plant  and  Its  Products 168 

Importance,  Composition,  Ash,  Growth,  Structure, 
Chemical  Changes,  Enzymes,  Roots,  Stem,  Leaf,  Flower 
and  Fruit,  Nutrition,  Crops,  Harvesting,  Environment, 
Rotation 

VII    The    Soil •. 193 

Origin,  Formation,  Soil  Minerals,  Humus,  Pulverizing 
Agents,  Texture,  Physical  Properties,  Heat-absorbing 
Power,  Chemical  Properties,  Nitrification,  Retention  of 
Fertilizers,  Alkali  Soils,  Analysis 

7 


8        CHEMISTRY  OF  THE  FARM  AND  HOME 

Chapter  Page 

VIII    Fertilizers 214 

Classes,  Inspection,  Terms,  Values,  Home  Mixing,  Soil 
Amendment,  Application,  Choice  for  Specific  Crops, 
Systems 

IX    Farm  Manure 236 

Importance,  Source,  Amount,  Value,  Manurial  Value  of 
Feeding  Stuffs,  Manure  of  Different  Animals,  Urine, 
Losses,  Spreading,  Absorbents,  Preservatives,  Increasing 
Value,  Use,  Effects,  Green  Manuring,  Sewage 

X    The  Animal  and  Its  Products 262 

Parts,  Composition,  Nurtition,  Digestion,  Respiration, 
Assimilation,  Excretion,  Skin,  Kidneys,  Products,  Effi- 
ciency 

XI    The  Feeding  of  Animals 274 

Scientific  Foundation,  Nature  and  Composition  of  Feed- 
ing Stuffs,  Building  and  Fuel  Value,  Value  of  Indigestible 
Roughage,  Productive  Value  of  Feeding  Stuffs,  Nutritive 
Ratio,  Differences  in  Food  Requirement,  Ash  Constit- 
uents, Fuel  Needs,  Need  of  Proteins,  Feeding  Standards, 
Influence  of  Food,  Condimental  Feeding  Stuffs,  Feeding 
Stuff  Laws 

XII    Dairy  Products 296 

Importance,  The  Udder,  Specific  Gravity  of  Milk,  Chem- 
ical Composition  of  Milk,  Milk  of  Different  Animals, 
Milk  of  Different  Breeds,  Lactation  Period,  Feeding 
Stuffs,  Gases  of  Milk,  Decomposition  of  Milk,  Condensed 
Milk,  Cream,  Centrifugal  Method,  Butter,  Rancidity, 
Oleomargarine,  Overrun,  Buttermilk,  Cheese,  Composi- 
tio-i  of  Dairy  Products,  Butter  and  Cheese  Flavors 

XIII    Human  Food  and  Dietetics 314 

Dietetic  Needs,  Fuel  Needs,  Protein  Needs,  Food  Stuffs, 
Meats,  Milk,  Eggs,  Vegetables,  Cereals,  Fruits,  Ciders, 
Wines,  Vinegar,  Cooking,  Baking,  Toasting,  Cooking  of 
Vegetables,  Spices,  Flavors,  Beverages,  Balancing  Diet, 
Cost  of  Diet,  Preservation  of  Food,  Labels,  Food  Laws 


TABLE  OF  CONTENTS  9. 

Chapter  Page 

XIV     Miscellaneous  Materials  of  Importance  in  Daily  Life 338 

Cotton,  Flax,  Hemp,  Wool,  Silk,  Dyeing,  Dyes,  Cleaning, 
Bleaching,  Paints  and  Varnishes,  Cements  and  Mortars, 
Concrete,  Plaster,  Insecticides,  Fungicides,  Disinfectants 

Experiments 363 

Appendix 417 


CHEMISTRY 

OF 

The  Farm  and  Home 


CHAPTER  1 
GENERAL  INTRODUCTION 

Definition  of  Chemistry.  Chemistry  is  the  science 
which  deals  with  the  composition  of  matter  and  the  molecu- 
lar   changes    which    it    undergoes. 

Descriptive  chemistry  treats  of  the  natural  character 
of  different  substances,  their  properties,  uses,  and  their 
manipulation   in   the   laboratory. 

Theoretical  chemistry  endeavors  to  explain  the  facts 
of  chemical  phenomena  by  advancing  theories  and  dis- 
covering laws  to  show  the  relation  of  the  facts. 

Definition  of  Other  Terms.  A  science  is  the  organ- 
ized knowledge  of  a  particular  subject.  The  following 
are  examples:  chemistry,  physics,  botany,  physiology, 
zoology,  and  geology.  Botany  is  the  science  of  plants; 
zoology,  of  animals;  geology,  of  the  earth  and  its  evolution. 
All  these  sciences  deal  with  various  forms  of  matter.  Chem- 
istry, therefore,  must  be  closely  associated  with  these 
other  sciences. 

A  fact  is  a  truth.  It  may  be  known  or  unknown;  but, 
of  course,  in  science  we  are  limited  to  truths  which  have 


.:>,.  -  z  ^s%.^' 

12  'ik^Ml^'f^Y  'dp  ilh  FARM  AND  HOME 

been  experienced  and  proved.  Facts,  or  truths,  do  not 
change;  but  in  the  evolution  of  a  science  the  acceptance 
of  imperfectly  known  truth  for  fact  must  necessarily  be 
supplanted  by  further  experience  and  experiment.  Science 
grows. 

A  law  is  a  rule  which  expresses  the  manner  in  which 
substances  have  been  observed  to  react. 

An  hypothesis  is  a  supposition  without  proof  which  may 
result  in  the  discovery  of  a  law. 

A  theory  is  an  hypothesis  offered  in  explanation  of  the 
phenomena  of  nature  and  which  has  a  certain  amount  of 
scientific  demonstration  to  substantiate  it.  The  acquisi- 
tion of  new  facts  may  result  in  the  revision  or  rejection 
of  a  theory. 

Matter  is  anything  which  occupies  space.  It  also  has 
weight.  There  are  thousands  of  different  kinds  of  matter, 
existing  either  in  the  form  of  a  solid  or  a  liquid  or  a  gas, 
such  as  iron,  water,  and  air.  We  distinguish  between 
substances,  or  kinds  of  matter,  by  their  characteristics  or 
qualities,  which,  in  chemistry,  are  called  properties.  Is 
it  solid,  liquid,  or  gas?  Is  it  lighter  or  heavier  than  water? 
What  are  its  color  and  odor?  Does  it  burn?  Is  it  soluble 
in  water?  These  are  some  of  the  questions  which  refer  to 
the   properties   of   matter. 

Energy  may  be  defined  as  the  capacity  for  performing 
work.  In  other  words,  it  is  a  force  or  power.  Anything 
that  produces  motion  or  tends  to  change  motion  is  called 
a,  force.  Matter,  under  the  influence  of  a  force,  can,  there- 
fore, do  work  upon  other  matter,  and  is  said  to  "possess 
energy."  Some  examples  of  the  manifestation  of  energy 
are  heat,  light,  wind,  life  processes,  and  chemical  affinity, 
or  energy.  The  measure  of  the  work  performed  by  mo- 
tion is  the  product  of  the  force  by  the  distance  through 
which  the  force  acts. 

Chemical  energy  is  that  force  which    reacts   between 


INTRODUCTION  13 

different  substances  in  such  a  way  as  to  disintegrate  and 
reform  into  new  compounds.  In  the  change  energy  is  de- 
veloped. Chemical  energy  may  produce  light,  heat, 
electricity,  etc.,  or  these,  in  turn,  may  produce  chemical  en- 
ergy. Electricity  and  light  may  result  from  the  chemical 
change  in  a  battery.  Electricity  passed  through  oxygen 
and  hydrogen  causes  an  explosive  chemical  change  that 
creates  the  compound  water. 

Conservation  of  Matter  and  Energy.  In  all  physical 
and  chemical  changes  alike  there  is  no  loss  or  gain  of  mat- 
ter or  force.  Action  is  always  equal  to  reaction,  and  the 
weights  before  and  after  chemical  results  constitute  an 
equation.  Matter  is  indestructible  and  ''the  sum  total 
of  the  energy  of  the  universe  is  a  fixed  unalterable  quantity." 

Importance  of  Chemistry.  Chemistry  has  almost  end- 
less practical  bearing  on  everyday  life.  We  are  living 
beings.  What  are  the  secrets  of  life's  processes?  We 
breathe  the  air.  What  is  its  function?  We  drink  water 
and  eat  foods.  We  must.  Why?  How  do  they  become 
assimilated  and  manifest  their  energy?  We  build  houses 
out  of  wood  or  stone  and  mortar  and  glass.  All  these 
materials  are  the  products  of  chemical  processes. 

Medicine,  sanitation,  and  domestic  science  make  ex- 
tended use  of  chemistry.  The  important  manufacturing 
processes  of  iron  and  steel,  illuminating  gas,  paints,  soap, 
paper,  fertilizers,  etc.,  all  depend  upon  chemical  principles 
for  their  discovery  and  greatest  efficiency.  A  knowledge 
of  chemistry  is  also  necessary  for  the  intelligent  study  of 
the  other  natural  sciences. 

And  chemistry  cannot  be  excluded  from  the  farm. 
Practically  the  whole  subject  of  fertilizers  and  soil  conditions 
arid  productivity  is  in  the  domain  of  this  science.  The 
growth  of  the  crop,  the  diseases  that  may  attack  it,  insecti- 
cides and  fungicides,  successful  feeding  of  stock,  the  keeping 
of  milk,  and  the  making  of  butter  and  cheese  all  abound 


14 


CHEMISTRY  OF  THE  FARM  AND  HOME 


in  chemical  reactions.     To  the  chemist  is  due  a  large  share 
of  the  advance  in  scientific  farming. 

The  intimate  relationship  between  chemistry  and  agri- 
culture may  be  likened  to  that  of  a  hub  and  a  wheel. 
Using  this  comparison,  Figure  1  graphically  illustrates  some 

of  the  principal  features 
in  which  chemistry  has 
been  of  service  to  agri- 
culture. 

Chemistry  is  an  exact 
and  unalterable  science. 
Its  principles  operate 
whether  we  know  and 
believe  them  or  not. 
They  do  not  accommo- 
date themselves  to  us. 
We  must  put  ourselves 
in  harmony  with  them. 
It  behooves  us,  there- 
them.  We  are  sure  of 
We  are  sure  to  fail. 


Figure  1. — The  relationship  of  chemistry  and 
agriculture. 


fore,   to   study   and  understand 
success,  if  we  have  nature  on  our  side, 
if  it  is  against  us. 

Civilized  man  has  enlarged  his  life  by  giving  bodily  ex- 
istence to  the  secrets  of  chemistry  which  he  has  discovered. 
He  is  constantly  inventing  new  substances  which  minister 
to  his  need.  The  savage,  however,  in  his  ignorance  is 
content  with  his  primitive  hut  and  fire.  The  study  of 
chemistry,  then,  stimulates  the  imagination  and  contributes 
to  the  advancement  of  civilization. 

Elements  and  Compounds.  There  are  many  thousand 
different  kinds  of  matter.  Some  of  these  substances  are  very 
famihar  to  everybody,  for  example,  iron,  salt,  and  water. 
Other  substances  are  more  or  less  common,  as  muriatic  acid, 
while  hundreds  of  others  are  extremely  rare  and  only  known 
as  museum  specimens  or  those  secured  by  some  investigator 


INTRODUCTION  15 

in  his  studies.  These  great  quantities  of  different  materials 
consist  of  one,  two  or  more  different  kinds  of  matter.  Those 
that  it  is  impossible  by  any  known  means  to  decompose 
or  divide  into  simpler  fornis  of  matter,  differing  from  the 
original  substances,  are  elementary  and  are  called  elements. 
For  example,  pure  iron  cannot  be  decomposed  by  any  known 
means,  into  parts  differing  from  iron.  Iron  is  an  element. 
Those  substances  that  are  formed  by  the  chemical  union 
of  two  or  more  elements  are  called  compounds.  A  com- 
pound may  be  broken  up  by  chemical  means  into  the  ele- 
ments of  which  it  is  composed.  But  a  compound  cannot 
be  decomposed  by  mere  mechanical  subdivision  into  its 
elements.  For  example,  sulphur  and  iron  may  form  a 
compound  by  a  chemical  reaction.  This  compound  may  be 
decomposed  by  chemical  means  into  the  original  substances, 
iron  and  sulphur.  But  the  compound  cannot  be  separated 
by  siniple  mechanical  processes  into  iron  and  sulphur. 

At  present  there  are  about  eighty  elements  known  to 
chemists.  There  are  at  least  two  hundred  thousand  com- 
pounds which  have  actually  been  prepared  and  studied. 
Many  more  are  theoretically  possible.  In  Table  I  is  given 
a  list  of  two  dozen  elements  which  are  of  special  interest  in 
connection  with  the  study  of  everyday  life.  A  complete 
list  of  all  the  elements  is  given  in  the  Appendix. 

TABLE  I— A  Selected  List  of  24  Chemical  Elements  and  Their  Symbols 

Element  Symbol  Element  Symbol 

Aluminium Al  Mercury Hg 

Argon A  Nickel Ni 

Arsenic As  Nitrogen N 

Calcium Ca  Oxygen O 

Carbon C  Phosphorus P 

Chlorine CI  Potassium K 

Copper Cu  Silicon Si 

Gold Au  Silver Ag 

Hydrogen H  Sodium Na 

Iron Fe  Sulphur S 

Lead Pb  Tin Sn 

Magnesium Mg  Zinc Zn 


16  CHEMISTRY  OF  THE  FARM  AND  HOME 

Compounds  and  Mixtures.  It  is  necessary  to  distin- 
guish carefully  between  the  two  expressions,  compound 
and  mixture.  As  already  stated,  a  compound  is  formed  by 
the  chemical  union  of  elements.  But  a  mixture  is  formed 
by  merely  intermingling  two  or  more  substances,  without 
chemical  union.  The  constituents  of  a  compound  cannot 
be  separated  by  a  mere  mechanical  process;  but  the  com- 
ponents of  a  mixture  can  be  separated  in  this  manner.  For 
example,  a  mixture  of  iron  filings  and  sulphur  powder  may 
be  entirely  separated  by  using  a  sieve  of  the  proper  fine- 
ness. There  are  two  other  general  differences  between 
compounds  and  mixtures.  First,  in  a  compound  the  elements 
are  united  in  definite  proportions;  in  a  mixture  the  ingredi- 
ents may  be  present  in  any  proportion.  Second,  when  a 
compound  is  formed,  there  is  usually  some  change  of  ener- 
gy, as  the  liberation  of  light  or  heat;  when  a  mixture  is  pre- 
pared, there  is  usually  no  such  change  of  energy.  The 
number  of  mixtures  possible  is,  of  course,  infinite.  Mix- 
tures are  very  common  and  familiar.  The  soil  is  a  mix- 
ture of  a  large  number  of  minerals.  The  rock,  granite, 
is  a  mixture  of  a  number  of  minerals  such  as  quartz,  mica, 
feldspar,  and  hornblende.  Milk  is  a  mixture  of  water,  fat, 
sugar,  and  proteins,  with  some  mineral  matter. 

Abundance  of  Elements.  There  are  about  80  elements 
which  exist  in  nature.  It  is  interesting  to  note  the  relative 
predominance  of  these  substances.  Of  the  above  number 
there  are  only  eight  elements,  each  one  of  which  exists  in  the 
whole  terrestrial  globe  to  an  extent  of  one  per  cent  or  over 
by  weight.  Less  than  half  of  all  the  elements  are  ever  found 
free.     Less  than  half  are  common,  and  many  are  very  rare. 

It  has  been  estimated  that  the  surface  layer  of  the 
earth,  to  a  depth  of  ten  miles,  consists  of  approximately 
93%  solid  crust  and  7%  water.  The  atmosphere  is  about 
0.03%  of  the  total.  With  these  figures  as  a  basis,  and 
knowing  the  kind  and  amount  of  the  different  substances 


INTRODUCTION 


17 


present  in  the  surface  layer  mentioned,  it  is  possible  to  com- 
pute the  relative  amount  of  the'  different  elements  quite 
accurately.  Beyond  the  ten  mile  depth  it  would  be  possible 
only  to  speculate  as  to  the  composition  of  the  earth  mate- 
rials. Over  99%  of  the  matter  of  our  planet  is  made  up  of 
only  thirteen  of  the  elements,  united  in  various  compounds. 
The   other  elements   exist   in   relatively   small   quantities. 

TABLE  n — Average  Composition  of  the  Terrestrial  Globe 


Oxygen 

Silicon 

Aluminium 

Iron. 

Calcium 

Magnesium. ..'.... 

Sodium 

Potassium 

Hydrogen 

Carbon 

Chlorine 

Phosphorus 

Sulphur 

Nitrogen ,  .;.  . 

All  other  elements . 


Per  cent  of 

solid    crust 

(93%) 


47.07 

28.06 

7.90 

4.43 

3.44 

2.40 

2.43 

2.45 

.22 

.20 

.07 

.11 

.11 

'i!ii 


Per  cent 
of  ocean 

(7%) 


85.79 


.05 

.14 

1.14 

.04 

10.67 

.002 
2.07 


.09 


.008 


Average,  includ- 
ing atmosphere 

(100%) 


49.78 

26.08 

7.34 

4.11 

3.19 

2.24 

2.33 

2.28 

.95 

.19 

.21 

.11 

.11 

.02 

1.06 


100.00 


100.00 


100.00 


THE  EARTH 


THE  OCEAN 


3%^ 
THE  ATMOSPHERE 


Figure  2. — The  relative  abundance  of  the  elements. 

Figure  2    contains  three  simple  diagrams  which  show 
the  relative  abundance  of  the  elements  in  the  earth's  crust, 


18       CHEMISTRY  OF  THE  FARM  AND  HOME 

the  ocean,  and  the  atmosphere.  What  is  the  most  striking 
feature  illustrated  by  this  series  of  diagrams? 

Chemistry  and  Physics.  The  statement  was  made  in 
the  opening  paragraph  of  the  chapter  that  chemistry  is 
concerned  with  the  study  of  matter  and  the  changes  which 
matter  may  undergo.  There  is  another  science  which  is 
also  involved  in  such  studies,  but  from  a  different  point  of 
view.  That  science  is  physic^.  Chemistry  is  primarily 
interested  in  the  study  of  matter,  what  it  is  composed  of, 
its  characteristics,  and  the  products  into  which  it  may 
be  converted  by  certain  agencies  or  forces.  Physics,  on 
the  other  hand,  is  principally  concerned  with  the  subject 
of  energy  and  its  transformations.  The  difference  in  the 
field  of  these  two  sciences  may  be  expressed  in  the  follow- 
ing manner.  Physics  considers  especially  the  changes 
in  which  the  composition  of  the  substance  is  not  altered, 
while  chemistry  considers  those  changes  that  result  in  new 
substances.  It  is  true  that  a  certain  change  in  matter  may 
interest  both  the  chemist  and  the  physicist  inasmuch  as 
energy  may  be  consumed  or  produced  by  this  phenomenon. 
In  fact,  there  is  a  comparatively  new  science,  physical 
chemistry,  which  involves  both  chemistry  and  physics. 

Physical  and  Chemical  Changes.  Matter  may  undergo 
a  great  many  changes,  some  natural  and  some  artificial. 
The  change  of  water  to  ice  and  the  rusting  of  iron  take 
place  under  certain  natural  conditions.  The  smelting  of 
copper  ores  and  the  burning  of  fuel  are  artificial  conditions. 
It  is  easy  to  tell  that  there  has  been  a  change  in  each  of  these 
cases,  because  the  properties  of  the  substances  obtained  are 
different  from  those  of  the  substances  taken.  All  changes 
are  divided  into  two  classes,  physical  and  chemical.  Phys- 
ical changes  are  those  in  which  the  composition  of  the 
substance  is  not  affected.  It  is  possible  to  repeat  a  physical 
change  with  the  same  substance.  Examples  of  such  changes 
are  the  melting  of  ice  and  the  production  of  light  from 


INTRODUCTION  19 

incandescent  electric  lamps.  Chemical  changes  are  those 
in  which  the  composition  of  the  substance  is  involved. 
Examples  of  such  changes  are  the  burning  of  coal  and  the 
rusting  of  iron. 

Physical  and  Chemical  Properties.  In  describing  dif- 
ferent kinds  of  matter  and  the  results  of  their  changes  we 
make  use  of  the  properties  of  these  materials.  For  pur- 
poses of  convenience  the  properties  are  classed  as  either 
physical  or  chemical.     The  physical  properties  are 

1.  Form  or  state;  as  gas,  liquid,  or  solid.     This  varies  with  con- 

ditions  of   temperature   and   pressure. 

2.  Weight  or  specific  gravity.     This  is  the  weight  relative  to 

some  determined  standard 

3.  Color,    odor,    and    taste. 

4.  Electrical  characteristics. 

These  properties  can  be  determined  without  any  reaction 
or  chemical  change. 

The  chemical  properties  are 

1.  The  abihty  to  combine  with  other  elements  or  compounds, 

and  the  manner  in  which  the  combination  takes  place. 

a.  Active,  readily  uniting. 

b.  Inactive,  not  readily  uniting. 

c.  Active  with  certain  elements  and  under  certain  con- 

ditions; inactive  with  other  elements  and  under 
other  conditions. 

2.  The  products  formed  as  the  result  of  reactions. 

These  properties  can  be  shown  only  by  a  chemical  change. 
The  agricultural  scene  shown  in  Figure  3  illustrates 
a  number  of  applications  of  the  points  that  have  been  under 
discussion  in  this  chapter.  The  traction  engine  uses  oil, 
a  form  of  matter.  By  the  process  of  combustion  the  oil  is 
converted  into  other  products,  but  in  doing  so  a  large  amount 
of  heat  is  liberated.  Heat  embodies  energy  and  is  capable 
of  doing  work.  The  engine  is  able,  then,  to  proceed  through 
the  field  and  drag  the  gang  plows  or  other  implements  after 
it.     What  kind  of  change  takes  place  in  the  combustion 


20 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Figure  3. — An  agricultural  application  of  chemistry. 


chambers  of  the  engine?  What  kind  of  change  does  the 
plow  effect  in  the  soil?  What  kind  of  change  does  the  ex- 
posure of  fresh  portions  of  the  soil  to  the  air  bring  about? 
These  and  other  questions  naturally  suggest  themselves  to 
the  student. 

SUMMARY 

The  science  of  chemistry  treats  of  matter  and  the  changes  which 
matter  undergoes.  It  is  made  up  of  a  collection  of  facts,  laws,  and  theo- 
ries concerning  thousands  of  different  substances  and  phenomena 
and  the  effect  of  different  forms  of  energy.  Chemistry  is  a  subject 
of  great  interest  and  importance.  Its  principles  are  in  apphcation  in 
our  everyday  Hfe,  in  many  manufacturing  processes,  and  in  other  scien- 
ces. It  is  especially  of  practical  benefit  in  the  study  of  scientific  agriculture. 

There  are  about  eighty  elements  of  which  only  twenty-four  are 
common  in  our  daily  life.  There  are  thousands  of  compounds,  some 
of  which  occur  in  nature,  others  being  purely  artificial.  The  elements 
are  very  unequally  distributed.  Only  nine  occur  to  the  extent  of  one 
per  cent  or  over  of  the  earth. 

Several  sciences  are  closely  associated  with  chemistry.  There 
is  usually,  though,  some  more  or  less  definite  line  separating  the  field 
of  those  overlapping  subjects.  For  example,  both  physics  and  chem- 
istry deal  with  matter  and  the  changes  of  matter  induced  by  energy. 
But,  while  chemistry  takes  up  those  changes  that  result  in  new  sub- 


INTRODUCTION  21 

stances,  physics  considers  especially  the  changes  in  which  the  com- 
position of  the  substance  is  not  altered,  but  wherein  energy  is  concerned. 
In  other  words,  chemistry  concerns  matter  and  physics  concerns 
energy. 

QUESTIONS 

1.  Define   science,    fact,    theory. 

2.  Distinguish  between  the  meaning  of  the  following  pairs  of 
terms:  matter  and  energy;  element  and  compound;  compound  and 
mixture;  physical  change  and  cheniical  change. 

3.  Give  two  examples  of  chemical  change  (not  previously  men- 
tioned) and  show  how  it  can  be  proved  that  they  are  chemical  changes. 

4.  Classify  the  following  as  physical  or  chemical  changes:  the 
rusting  of  iron,  the  souring  of  milk,  the  melting  of  ice,  the  drying 
of  paint,  the  corrosion  of  metals,  the  magnetization  of  steel. 

5.  Give  a  list  of  properties  by  which  matter  may  be  recognized. 

6.  What  properties  could  you  make  use  of  to  distinguish  between 
salt  and  sugar? 

7.  Why  should  everyone  know  something  about  the  science  of 
Chemistry? 

8.  If  there  are  other  sciences,  just  what  is  the  particular  field  of 
Chemistry? 

9.  What  is  the  essential  difference  in  the  scope  of  the  two  sciences. 
Chemistry  and  Physics, 


CHAPTER  II 

WATER  AND  ITS  CONSTITUENT  ELEMENTS 
WATER 

Introduction.  Water  is  of  the  greatest  importance  to 
mankind.  It  is  one  of  the  most  abundant  chemical  com- 
pounds and  has  taken  an  active  part  in  the  formation 
of  the  earth's  surface.  Climatic  conditions  are  modified 
by  the  presence  of  water.  It  is  one  of  the  controlling  fac- 
tors of  plant  life  and  animals  cannot  exist  without  it.  Cer- 
tain industries  depend  upon  water  for  their  successful 
operation.  It  is  a  valuable  source  of  power  both  for  gener- 
ating steam  and  as  waterfalls.  On  account  of  these  facts 
and  because  water  is  already  more  or  less  familiar  to  the 
student,  we  will  begin  our  study  of  chemistry  with  a  con- 
sideration of  this  substance. 

Distribution.  Water  occurs  free  in  nature  in  large 
bodies,  such  as  oceans,  lakes,  and  rivers,  which  cover  about 
eight  elevenths  of  the  surface  of  the  earth.  It  is  also  dis- 
tributed in  the  form  of  smaller  bodies  Hke  rivulets,  springs, 
brooks  and  underground  sources.  It  is  also  present  in  soils. 
Water  is  one  of  the  most  important  constituents  of  the 
atmosphere.  It  may  be  present  there  either  as  invisible 
vapor  or  as  clouds  and  fogs,  which  are  really  aggregates 
of  minute  drops  of  liquid   water. 

From  50  to  90  per  cent,  or  on  an  average  about  three 
fourths,  of  the  weight  of  living  matter,  both  plant  and  animal, 
is  water.  In  these  instances  water  niay  be  present  as 
circulating  water  of  vegetation,  or  sap,  and  as  the  chief 
constituent  of  the  animal  body  fluids;  also  in  the  combined 
form  mentioned  below.  The  amount  of  moisture  present 
varies  widely  in  the  limits  indicated.     There  is  given  in 

22 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  23 

Table  III  a  list  of  a  few  typical  vegetable  and  animal  products 
and  their  content  of  water. 

Table  III. — Amount  of  Water  in  Certain  Natural  Products 

Per  Cent  Per  Cent 

Green  red  clover  hay 70  Milk 85 

Cucumbers 96  Blood 80 

Potatoes 78  Trout 78 

Wood 50  Fat  pig 41 

Turnip 90  Lean  pig 55 

Fruits .80  Jelly  fishes 99.5 

In  addition  to  the  free  water  held  by  the  living  cells, 
the  elements  of  which  water  is  composed,  hydrogen  and 
oxygen,  are  combined  with  the  other  elements  which  enter 
into  the  composition  of  plant  and  animal  bodies.  When 
such  substances  are  heated,  they  are  usually  decomposed. 
If  the  products  of  decomposition  are  collected,  water  can  be 
proved  to  be  present. 

Almost  all  vegetable  matter  in  the  finely  cut  condition 
or  even  when  uncut,  contains  a  certain  amount  of  moisture, 
called  hygroscopic  moisture,  which  it  has  absorbed  from 
the  atmosphere.  The  amount  of  this  moisture  varies  with 
climatic  conditions,  such  as  the  amount  of  moisture  in 
the  air  and  the  temperature. 

Many  mineral  substances  contain  large  quantities  of 
water  combined  in  their  structure.  This  may  very  easily 
be  shown  by  heating  some  clay  or  rock  powder  or  epsom 
salts  in  a  test  tube.  Water  is  liberated  and  condenses  in 
drops  on  the  cooler  portion  of  the  glass.  In  many  cases 
the  presence  of  this  water  is  responsible  for  the  character- 
istic crystalline  shape  and  other  properties  of  the  material. 
Blue  vitriol,  copper  sulphate,  for  example,  is  ordinarily  a 
crystalline  blue  solid.  Alum  is  an  octahedron,  an  eight- 
sided  crystal,  which  has  the  appearance  of  two  pyramids 
with  their  bases  placed  together.  Both  of  these  substances, 
when  heated  to  a  high  temperature,  lose  the  water  which 
is  combined  with  them,  and  become  white  powders. 


24 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Figure  4. — Graphic  representation  of  the  composition 
of  a  potato. 


It  is  necessary  to  note  in  this  connection  that  all  crystal- 
line compounds  do  not  contain  water  of  crystaUization. 
Salt  and  sugar  are  the  most  common  examples  of  such  ex- 
ceptions. Any  water  found  in  common  salt  is  either  held 
there  mechanically  between  the  crystals  or  else  is  moisture 
absorbed  from  the  atmosphere. 

Figure  4  shows  graphically  the  amount  of  water  and 
solids,  such  as  starch  and  other  constituents,  in  the  potato. 

This  may  be  re- 
garded as  a  fairly 
typical  illustra- 
tion of  the  distri- 
bution of  water 
in  the  plant  king- 
dom. 

Kinds  of  Wa- 
ter. Pure  water, 
as  will  be  shown, 
is  a  compound  of  two  elements,  hydrogen  and  oxygen.  In 
the  pure  form  it  practically  never  occurs  in  nature.  Natural 
waters  contain  impurities  which  differ  considerably  in  char- 
acter. Some  of  these  foreign  matters  are  visible  to  the  eye 
and  are  merely  suspended  in  the  water,  such  as  algae,  vege- 
table matter,  and  dust.  Other  impurities  are  invisible 
and  dissolved  in  the  water,  such  as  gases  and  salts.  The 
nature  of  these  suspended  and  dissolved  materials  is  very 
different,  depending  upon  the  conditions  through  which 
the  water  has  passed.  Some  of  the  principal  factors  affect- 
ing the  composition  of  water  are  (1)  substances  present  in 
the  air,  (2)  the  character  of  rocks  and  soils  over  which  the 
water  has  coursed,  and  (3)  the  opportunities  the  water 
has  had  of  losing  material  previously  gathered,  as  by  set- 
tling or  oxidation.  Hence  the  character  of  any  given  nat- 
ural water  is  dependent  mainly  upon  the  part  of  the  natural 
circuit  at  which  the  sample  of  water  in  question  is  taken. 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  25 

Rain  water  is  the  purest  water  that  can  be  found  in  nature, 
because  it  is  condensed  water  vapor.  Yet  rain  contains 
some  impurities  gathered  from  the  atmosphere.  The 
first  portions  of  a  rainfall  dissolve  certain  gases  and  wash 
the  dust  particles  down  to  the  earth.  After  it  has  rained 
for  a  time,  the  most  of  these  gaseous  impurities  have  been 
removed  from  the  air.  Consequently  the  later  rainfall 
is  fairly  free  from  the  substances.  On  the  other  hand 
all  natural  waters  contain  nitrogen,  oxygen  and  carbon 
dioxide  dissolved  in  them.  These  are  not  to  be  regarded 
as  impurities  from  the  hygienic  sense,  but  they  are,  of 
course,  impurities  in  the  strictly  chemical  sense.  They 
give  taste  and  zest  to  the  water.  Most  persons  notice  the 
difference  of  flavor  between  boiled  water  and  fresh  water. 
It  is  the  presence  of  the  dissolved  oxygen  in  the  fresh  water 
which  makes  the  difference. 

Soil  water  contains  those  substances  which  are  easily 
dissolved  by  rain.  These  soluble  materials  may  be  taken 
up  by  plants  and  utilized  by  them  in  their  growth  or  they 
may  drain  off  into  rivers  or  ground  waters. 

Spring  water  may  contain  a  considerable  amount  and 
often  a  great  variety  of  dissolved  minerals.  These  also 
are  derived  from  the  rocks  and  soil  through  which  the 
water  has  filtered.  Such  water  usually  contains  a  large 
amount  of  gases  which  are  liberated  as  soon  as  the  water 
reaches  the  surface  of  the  ground.  One  of  these  gases, 
carbon  dioxide,  partly  increases  the  solvent  action  of  the 
rain  upon  the  rock  material.  In  this  way  large  quantities 
of  limestone  are  found  in  solution  where  limestone  predom- 
inates in  the  earth's  crust.  The  great  advantage  of  spring 
water  is  its  purity  from  disease  germs  and  organic  matter. 

River  water  contains  materials  both  in  solution  and  in 
suspension  which  it  has  secured  from  soil  and  rocks  and  the 
atmosphere.  Rivers  are  merely  large  currents  of  spring 
water.    The  springs  feed  a  river  by  either  pouring  into  its 


26  CHEMISTRY  OF  THE  FARM  AND  HOME 

current  from  the  banks  or  else  helping  to  swell  the  tributary- 
streams.  The  river  water  has  absorbed  some  of  its  impur- 
ities by  its  contact  with  the  surface  of  the  earth  and  by  the 
smaller  streams  that  pour  into  it.  This  indicates  that 
river  water  is  not  as  pure  as  spring  water.  It  is,  on  the 
other  hand,  very  soft  as  compared  with  spring  water  and  is, 
therefore,  more  healthful,  if  it  is  free  from  disease  germs. 

Sea  water  and  salt  lakes  contain  the  most  impurities 
of  any  natural  water.  The  rivers  are  constantly  bringing 
to  the  ocean  new  supplies  of  salts  dissolved  from  the  land. 
The  oceans,  therefore,  are  the  great  storehouses  of  all  natural 
salts.  Hardly  a  substance  can  be  named  which  is  not 
found  to  a  certain  extent  in  sea  water.  Attempts  have 
been  made  to  extract  even  the  gold  that  is  present  in  these 
waters.  The  extremely  small  quantities  of  this  valuable 
metal,  however,  present  a  great  difficulty  in  recovery. 

A  convenient  classification  for  natural  waters  is  given 

below.    This  shows  in  condensed  form  the  differences  in 

the  amount  and  character  of  the  impurities  of  water. 

fRain — some  gases,  very  little  dissolved  solids. 
Atmospheric. . .  .-(Snow — dust,  etc. 

[Fog — some  gases,  dirt  and  dust. 

(Surface — cloudy,  small  amount  of  dissolved  mate- 
rial, large  amount  of  suspended  material. 
Underground— clear,  large  amount  of  diss9lved  ma- 
terial, small  amount  of  suspended  material. 

T-«.«.««+,;„i   QoU     /Brines — over  5%  soluble  salts. 
Terrestrial,  Salt.  .<^g^^  water-3.6%  soluble  salts. 

Terrestrial,  Mineral — Excess  of  dissolved  gases  and  mineral  matter. 

Circulation  of  Water.  There  is  a  constant  circulation 
of  water  in  nature.  This  so-called  cycle  can  be  represented 
by  a  diagram  (see  Figure  5)  where  the  different  stages  are  in- 
dicated at  different  positions  upon  a  circle.  By  evapora- 
tion from  large  bodies  of  water  and  soils,  by  the  transpiration 
of  plants,  and  the  respiration  of  animals  water  passes  into 
the  atmosphere  in  the  form  of  a  vapor.  Under  certain 
conditions  this  vapor  condenses,  forming  clouds  and  fogs, 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  27 

and  returns  to  the  earth's  surface  in  the  form  of  rain.  Mois- 
ture may  also  be  precipitated  from  the  atmosphere  in  the 
form  of  snow,  sleet,  hail,  dew  and  frost.  From  the  surface 
of  the  earth  the  water  may  go  in  any  of  three  directions. 
First,  it  runs  off  directly  downward  over  the  land  into  brooks 
and  rivers.  This  is  surface  drainage  and  is  sometimes 
called  the  run-off.  Second,  part  is  retained  as  the  ground 
water  of  soils  and  part  sinks  deeply  into  subterranean 
cuouDs  supplies  of  .water. 

This     is      under- 
uAKEs.ncDCEANsX       /   '.       x«AiNrAL.i.  ground     drainage 

and  is  called  the 
cut-off.  Such  wat- 


ers often  come  to 

the  surface  again 

suRrActwATER^V  ^cRouNo WATERS    through  natural 

Figure  5.-The  cycle  of  water.  fisSUrCS,^     aS     min- 

eral springs,  or  by 
artificial  openings  as  in  the  case  of  wells.  Third,  a  portion 
may  pass  up  from  the  land  by  evaporation  into  the  atmos- 
phere. This  has  been  called  the  fly-off.  The  rivers  flow 
into  the  oceans  and  from  there  the  cycle  may  start  again, 
being  constantly  repeated.  Certain  portions  of  water  need 
not  necessarily  pass  through  all  the  stages  of  the  circuit 
as  indicated  above.  Some,  for  example,  may  continually 
pass  and  repass  between  land  and  atmosphere  without 
ever  finding  its  way  into  the  ocean;  the  most  of  the  moisture 
evaporated  from  the  ocean  and  condensed  as  rain  returns 
to  the  ocean  through  rivers;  and  some  may  be  diverted 
to  salt  lakes.  This  ceaseless  round  continues  as  long  as  the 
sun  furnishes  the  needed  energy.  Thus  all  water  power  is 
really  derived  from  the  sun. 

Purification  of  Water.  As  has  been  already  indicated, 
practically  all  natural  waters  are  more  or  less  impure. 
The  materials  which  may  be  present  are  either  solid  sub- 


2S 


CHEMISTRY  OF  THE  FARM  AND  HOME 


stances  in  suspension,  or  gases  and  solids  in  solution.  In 
order  to  purify  the  water  for  drinking  or  for  industrial  and 
household  uses,  these  materials  must  be  removed.  There 
are  a  number  of  methods  which  can  be  used  for  this  purpose, 
but  the  choice  of  method  depends  upon  the  character  of 


Figure  6. — Cross-section  of  a  water  purification  plant. 

the  water  and  the  use  to  which  it  is  to  be  put.  Simple 
filtration  of  water  may  be  sufficient  to  remove  soUd  impur- 
ities. This  may  be  accomplished  by  a  charcoal  filter,  by  a 
sand  filter,  or  by  a  layer  of  any  other  material,  which  will 
serve  to  aerate  the  water  and  remove  the  bacteria,  dirt  and 
other  suspended  foreign  matter  present.  Quite  a  few 
examples  of  such  mechanical  filters  are  found  in  the  house- 
hold and  in  the  large  city  water-filtration  plants. 


WATER  AND  ITS  CONSTITUENT  ELEMENTS 


29 


Boiling  may  accomplish  a  partial  purification  of  the 
water  by  expelling  gases  in  solution,  killing  bacteria,  and 
causing  such  substances  as  limestone  to  be  precipitated 
from  the  solution.    The   addition   of   chemicals,  such   as 

milk  of  lime,  alum,  and 
sulphate  of  iron,  may 
also  partially  purify  wa- 
ter for  both  household 
and  industrial  uses  by 
precipitating  the  lime- 
stone and  other  impur- 
ities which  are  dissolved 
in  the  water.  A  cross- 
section  of  a  commercia- 
plant  used  for  this  pure 
pose  is  shown  in  Figur- 
6.  Distillation,  how- 
ever, is  the  only  methl 
od  for  producing  water 
which  is  practically 
pure  and  free  from  all 
foreign  matter.  The 
general  term  distilla- 
tion applies  to  a  process  in  which  a  liquid  is  heated  and 
changed  to  a  vapor,  which  in  turn  is  cooled  and  condensed 
to  a  liquid.  Figure  7  shows  a  laboratory  still.  In  the 
case  of  water,  the  first  portions  (about  one  fifth)  of 
the  condensed  liquid  can  be  discarded,  since  they  con- 
tain some  of  the  gaseous  impurities  of  the  original 
water.  Also  the  last  portion  {}^i)  of  the  original  quantity 
which  contains  all  the  salts  is  left  in  the  still.  The  distillate 
that  comes  over  between  these  portions  is  the  pure  water 
which  is  desired. 

River  water  may  gather  considerable  organic  impur- 
ities as  it  passes  over  its  course.     In  this  refuse  material 


Figure  7.     A  laboratory  still. 


30      CHEMISTRY  OF  THE  FARM  AND  HOME 

of  plant  and  animal  origin  there  may  be  some  micro-organ- 
isms. Some  of  these  may  be  the  common  bacteria  char- 
acteristic of  sewage,  for  example,  or  manure  piles,  or  even 
of  certain  diseases.  If  the  river  is  sluggish,  these  impurities 
are  not  removed  readily.  But,  if  the  river  has  a  swift  cur- 
rent and  especially  if  there  are  rapids  and  waterfalls  in 
its  course,  the  water  soon  purifies  itself  by  bringing  its  im- 
purities into  contact  with  the  oxygen  of  the  air,  which 
destroys  them.  The  sewage  of  Chicago  is  emptied  into 
the  Illinois  river.  After  flowing  300  miles,  this  empties 
into  the  Mississippi  a  few  miles  above  the  point  from  which 
St.  Louis  takes  its  water  supply.  This  seems  to  be  a  danger- 
ous procedure,  but  it  has  been  proved  that  this  water  has 
no  more  bacteria  than  neighboring  rivers  which  do  not  re- 
ceive sewage.  In  addition  to  the  oxidation  already  men- 
tioned, it  is  possible  that  the  bacteria  consume  the  sewage 
very  quickly  and  then  die  for  lack  of  food.  They  may  also 
be  devoured  by  other  organisms  or  killed  by  the  sunlight. 

Physical  Properties.  Water,  when  pure,  is  an  odorless 
and  tasteless  liquid,  colorless  in  small  masses  but  pale 
greenish  blue  when  seen  in  considerable  thickness.  In 
this  respect  it  is  quite  similar  to  an  ordinary  window  pane 
of  glass.  It  is  a  poor  conductor  of  heat  and  electricity. 
Water  dissolves  many  soUds,  liquids,  and  gases.  It  is  in 
fact   the  most   common   solvent   known. 

Water  is  probably  the  most  familiar  example  of  a  sub- 
stance that  can  exist  in  three  states  of  matter  without 
change  of  composition.  It  is  a  gas,  commonly  called  steam, 
above  100°C.,  a  liquid,  water,  between  0°  and  100°C., 
and  a  solid,  ice,  below  0°C.  In  its  passage  from  one  state 
to  another,  considerable  heat  may  be  liberated  or  absorbed 
as  the  case  may  be.  In  passing  into  the  gaseous  state, 
a  gram  of  water  absorbs  537  calories*  and  expands  from 


*A  calorie  is  the  quantity  of  heat  necessary  to  raise  1  gram  of  water  from   0° 
to  1°C. 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  31 

1  to  1,728  volumes.  In  other  words,  a  cubic  inch  of  water 
will  make  a  cubic  foot  of  steam.  Water  will,  however, 
become  a  vapor  at  all  temperatures  depending  upon  whether 
the  surrounding  atmosphere  is  saturated  or  not.  In  the 
liquid  form  water  is  practically  incompressible,  a  property 
which  is  of  use  in  the  well  known  hydraulic  press.  But 
when  a  gram  of  liquid  water  becomes  ice,  it  expands  10%  and 
liberates  79  calories.  This  phenomenon  is  responsible  for  a 
great  many  burst  water  pipes,  the  splitting  of  rocks,  and 
the  heaving  effect  of  frost  in  the  ground.  Because  water 
expands  in  freezing,  ice  is  lighter  than  water  and  floats. 

Water  is  used  as  a  standard  of  weight,  1  cubic  centimeter 
at  4°C.  being  called  1  gram.  The  boiling  point  and  freez- 
ing point  of  water  are  used  as  convenient  points  for  stand- 
ardizing thermometer  scales;  on  the  Centigrade,  100° 
and  0°  respectively;  on  the  Fahrenheit  212°  and  32°.  As 
a  standard  unit  of  specific  gravity  measurements,  water 
serves  both  for  soHds  and  liquids.  The  hydrometer  floats 
at  1  in  distilled  water  of  15.5°C.  On  the  Baum6  scale 
water  is  marked  at  0. 

Solution.  The  importance  of  water  as  an  agent  for 
dissolving  different  kinds  of  matter  is  very  apparent.  In 
the  discussion  of  the  cycle  of  water,  reference  has  been  made 
to  this  action.  We  will  now  consider  briefly  a  few  general 
points  in  connection  with  the  character  of  solution.  The 
substances  concerned  are  mixed  in  such  a  way  that  the 
matter  of  each  is  distributed  uniformly  through  that  of 
the  others.  The  expression  homogeneous  mixture  can  be 
used  to  designate  this  condition,  that  is,  every  part  of  the 
mixture  is  composed  of  the  same  kind  and  quantity  of  matter. 
If  this  term  were  considered  broadly,  it  might  include  a 
large  number  of  phenomena,  but  it  is  usually  restricted 
to  the  absorption  of  a  gas,  a  liquid,  or  solid,  within  the 
space  occupied  by  some  Hquid.  The  liquid  is  called  the 
solvent.     The  dissolved  material  is  called  the  solute.     The 


32 


CHEMISTRY  OF  THE  FARM  AND  HOME 


most  common  solvent  is  water,  though  alcohol  and  ether 
are  also  common,  especially  in  drug  preparations.  Water 
dissolves  nearly  all  substances  to  an  appreciable  extent. 
The  permanent  tissues  of  plants  and  animals,  India  rubber, 
resins  and  some  other  substances  are  practically  insoluble. 
Soluble  and  insoluble  are  merely  relative  terms,  since 
there  is  probably  no  substance  of  which  a  small  amount 

will  not  dissolve,  if  the  quan- 
tity of  the  solvent  is  large 
enough.  Generally  speaking, 
readily  soluble  is  applied  to  a 
substance  that  requires  less 
than  100  times  its  weight  for 
complete  solution;  difficultly 
soluble,  between  100  and  1,000 
times;  and  insoluble,  when 
more  than  1,000  parts  of  the 
solvent  are  required. 

The  term  solubility,  when 
applied  to  a  substance,  means 
the  maximum  amount  of  that 
material  that  can  be  taken 
up  by  a  given  quantity  of  the 
solvent  under  the  given  con- 

.  ditions.    The  student  is  prob- 

l"^  jo^  T^  0*^  3§^  imf  ably  already  aware  that  sub- 
stances differ  greatly  in  their 
degree  of  solubility.  He  also 
knows  that  temperature  has 
a  decided  influence  upon  the 
amount  of  a  substance  that  can  be  dissolved.  As  a  rule, 
the  higher  the  temperature,  the  greater  the  amount  of  solids 
dissolved,  but  the  less  the  amount  of  gases. 

A   comparison   of    two    household    articles    illustrates 
these  points  iii  connection  with  the  varying  solubility  of 


COMMON  SALT 


V 

SUGAR 


Figure  8. 


-The  solubility  of  salt  and 
sugar. 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  33 

chemical  materials.  Common  salt  is  nearly  as  soluble 
in  cold  water  as  in  hot.  Sugar,  on  the  other  hand,  is  much 
more  soluble  than  salt  and  increases  in  solubility  very 
strikingly  as  the  temperature  is  raised.  Figure  8  very 
clearly  shows  such  differences  in  solubility.  The  figures 
indicate  the  number  of  grams  of  material  dissolved  in  100 
cubic  centimeters  of  water  at  the  temperatures  given  on 
the  Centigrade  scale. 

The  specific  gravity  of  solutions  of  solids  is  greater  than 
that  of  the  solvent.  Substances  in  solution  raise  the  boil- 
ing point  and  lower  the  freezing  point  of  the  solvent.  When 
small  quantities  of  substances  are  dissolved  in  a  solvent, 
there  is  apparently  no  increase  of  volume.  There  is  usually 
an  evolution  of  heat  and  increase  of  temperature  when  a 
gas  dissolves  in  a  liquid.  But  the  solution  of  a  solid  is 
usually  attended  by  an  absorption  of  heat  and  a  reduction 
of  temperature,  though  there  are  certain  exceptions. 

The  solubility  of  gases  depends  not  only  upon  tem- 
perature but  also  upon  pressure.  Generally  an  increase 
of  temperature  means  a  decrease  of  the  quantity  of  gas 
dissolved,  though  there  are  exceptions  to  this  rule.  An 
increase  of  pressure  increases  the  solubility  of  gases.  Car- 
bonated waters  of  the  soda  fountain  are  the  most  common 
example,  where  a  large  amount  of  gas  has  been  forced  into 
water  and  kept  there  under  pressure.  When  the  stopper 
is  removed  from  the  bottle,  there  is  a  rapid  escape  of  the 
gas  on  account  of  the  reduced  pressure.  Certain  natural 
waters  exhibit  the  same  characteristic. 

The  solubility  of  gases  varies,  depending  upon  the 
character  of  the  gas.  Some  are  only  very  slightly  soluble 
while  others  are  exceptionally  so.  For  example,  100  volumes 
of  water  at  0°C.,  dissolve  only  5  volumes  of  oxygen,  but 
nearly  115,000  volumes  of  ammonia. 

Chemical  Properties.  Water  is  a  very  stable  sub- 
stance; in  other  words  it  does  not  decompose  readily.     Al- 


34 


CHEMISTRY  OF  THE  FARM  AND  HOME 


though  it  can  be  decomposed  into  its  elements  by  heat  alone, 
it  requires  a  very  high  temperature.  At  2,500°C.,for  exam- 
ple, only  about  5%  of  the  entire  amount  is  decomposed. 
It  is  possible  to  break  up  water  into  its  constituent  elements 
by  the  electric  current  and  by  some  chemical  methods. 

Electrolysis,  which  means  a  tearing  apart  by  means  of 
electricity,  is  the  simplest  method  and  the  one  most  easily 

demonstrated  for  decomposing 
water.  This  method,  moreover, 
has  the  advantage  of  showing 
some  facts  in  relation  to  the 
composition  of  water.  The  pro- 
cess is  carried  out  as  follows:  A 
current  from  an  electric  battery 
is  passed  between  platinum  elec- 
trodes through  water  containing 
about  5%  of  its  weight  of  sul- 
phuric acid.  While  the  current 
is  passing,  bubbles  of  gas  rise 
from  the  electrodes  up  through 
the  liquid.  The  gases  may  be 
collected  separately  by  inverting 
over  each  electrode  a  tube  filled 
with  the  dilute  acid.  The  rates 
at  which  the  two  gases  collect 
are  not  the  same.  The  one  at 
the  negative  electrode  collects  a  little  more  than  twice  as 
rapidly  as  the  other.  The  former  is  called  hydrogen  and 
the  latter  is  called  oxygen.  Figure  9  shows  the  nature  of 
the  apparatus  used  to  demonstrate  the  electrolysis  of  water. 
The  relation  between  the  volume  of  the  two  gases  is 
really  two  parts  hydrogen  and  one  part  oxygen.  The  ratio 
is  generally  slightly  larger  on  account  of  several  errors, 
one  being  that  the  oxygen  is  more  soluble  in  the  liquid 
than  is  the  hydrogen.    Water  itself  is  a  poor  conductor  of 


Figure  9 — The  electrolysis  of  water. 


WATER  AND  ITS  CONSTITUENT  ELEMENTS 


35 


electricity  and  is  not  electrolyzed.  The  purpose  of  adding 
the  sulphuric  acid  is  to  serve  as  a  carrier  for  the  electricity. 
The  water,  however,  is  the  substance  which  is  actually 
decomposed  by  the  process. 

From  the  electrolysis  of  water,  therefore,  two  substances 
are  obtained  that  are  gases  at  ordinary  conditions.  They 
are  different  from  water  in  their  properties  and  different 

from  each  other.  One  is  a  gas 
which  burns,  but  does  not  sup- 
port combustion.  The  other  is 
a  gas  which  supports  combus- 
tion, but  does  not  burn.  The 
first  is  called  hydrogen,  because, 
when  it  burns,  water  is  formed. 
The  word  hydrogen  comes  from 
two  Greek  words  meaning  "to 
generate  water."  The  other  gas 
is  called  oxygen,  meaning  ''acid 
producer,"  also  derived  from  the 
Greek.  These  will  be  studied 
more  in  detail  after  the  subject 
of  water. 

That  the  electrolysis  of  water 
is  an  important  commercial  pro- 
cess is  shown  by  the  fact  that 
this  operation  is  carried  on  at  the  present  time  upon  an 
enormous  scale.  Figure  10  illustrates  the  cross  section  view 
of  one  type  of  an  electrolytic  cell  and  Figure  11  shows  a 
battery  of  these  cells  used  for  generating  large  quantities  of 
oxygen  and  hydrogen. 

Action  of  Metals.  Water  may  also  be  decomposed 
by  coming  in  contact  with  certain  metals.  Cold  water 
reacts  directly  with  a  metal  called  potassium.  A  gas  is 
liberated  which  proves  to  be  the  same  as  one  of  those  from 
the   electrolysis   of   water.    The   potassium   disappears   in 


Figure  10. — An  electrolytic  cell  for 
decomposing  water. 


36  CHEMISTRY  OF  THE  FARM  AND  HOME 


Figure  11. 


-A  battery  of  electrolytic  cells  for  the  commercial  production  of 
hydrogen  and  oxygen. 


the  reaction  and  the  liquid  entirely  changes  its  properties. 
It  is  now  soapy  to  the  touch,  has  a  bitter  taste,  and  turns 
red  litmus  paper  blue.  Another  metal,  sodium,  acts  in 
the  same  way  as  potassium.  The  intensity  of  the  re- 
action is  not  so  great.  Two  other  metals,  lithium  and 
magnesium  decompose  hot  water  and  red  hot  iron  decom- 
poses steam.  The  reaction,  therefore,  can  take  place 
with  several  metals,  if  the  temperature  of  the  water  or  the 
condition  of  the  water  is  changed  to  conform  to  the  par- 
ticular metal  used. 

These  experiments  may  be  carried  on  in  such  a  man- 
ner that  the  gas  given  off  from  the  reacting  materials  can 
be  collected  in  a  proper  manner  and  its  properties  learned. 
If  a  small  piece  of  sodium,  for  example,  is  placed  at  the 
mouth  of  a  test  tube  full  of  water  inverted  in  a  beaker  of 
water,  the  sodium  at  once  rises  to  the  top  of  the  tube  and 
commences  to  react  with  the  liquid.  Th^t  a  gas  is  given 
off,  is  at  once  apparent;  for  the  volume  of  water  is  pushed 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  37 

out  of  the  tube  in  proportion  to  the  amount  of  the  metal 
taken  in  the  experiment.  After,  the  reaction  is  completed, 
the  tube  and  its  contents  of  water  and  gas  can  be  removed 
from  the  beaker  by  placing  the  thumb  over  th6  opening 
of  the  tube.  The  tube  is  inverted  into  its  normal  con- 
dition and  a  lighted  match  is  held  to  the  mouth.  The  gas 
either  burns  or  a  sHght  explosion  results  from  the  admixture 
of  the  air.  In  this  way,  it  can  be  proved  that  the  gas  is 
the  same  as  that  liberated  in  the  greatest  quantity  by  the 
electrolysis  of  water.     In  other  words  it  is  hydrogen. 

Action  of  Chlorine.  Certain  other  substances  decom- 
pose water,  liberating  the  other  constituent,  which  we  have 
already  found  by  electrolysis.  This  may  readily  be  shown 
by  filling  a  long  tube,  closed  at  one  end,  with  a  strong  solu- 
tion of  chlorine  in  water.  Invert  the  tube  in  a  glass  contain- 
ing the  same  solution  and  place  the  whole  apparatus  in 
bright  sunlight.  Bubbles  of  a  gas  will  soon  rise  and  collect 
in  the  tube.  It  can  be  proved  that  this  gas  is  oxygen,  by 
holding  a  glowing  splinter  of  wood  at  the  mouth  of  the 
tube,  after  sufficient  gas  is  collected  for  a  test.  The  chlo- 
rine has  a  more  powerful  attraction  for  the  hydrogen  of 
the  water  than  the  oxygen  has,  hence  chlorine  combines 
with  the  hydrogen  and  liberates  the  oxygen.  The  prin- 
ciple of  this  reaction  is  very  important  and  will  be  referred 
to  again  under  the  head  of  bleaching.  Fluorine,  an  element 
which  is  similar  to  chlorine  but  even  more  active  than  chlo- 
rine,  has  the  same  effect  upon  water. 

Water  as  a  Chemical  Agent.  As  a  chemical  agent,  water 
is  extremely  powerful,  acting  usually  as  a  solvent  but  in 
many  cases  producing  profound  changes  of  a  chemical 
character.  Many  anhydrous  substances  combine  with 
water,  when  crystallizing.  The  water  so  added  is  called 
water  of  hydration  or  water  of  crystallization.  The  presence 
of  the  water  in  the  structure  of  these  compounds  entirely 
changes   their   properties.     Copper   sulphate,    when   anhy- 


38       CHEMISTRY  OF  THE  FARM  AND  HOME 

drous  (that  is,  without  water),  is  a  yellowish  white  powder. 
One  drop  of  water  changes  this  immediately  to  a  pale  blue 
color.  Alum,  when  anhydrous,  does  not  give  its  char- 
acteristic taste  when  applied  to  the  tongue.  One  drop 
of  water  instantly  restores  the  peculiar  effect  of  that  com- 
pound upon  the  tongue.  QuickUme,  when  slaked  with 
water,  combines  directly  with  it,  giving  off  considerable 
heat  and  forming  milk  of  lime.  These  are  examples  of 
the  direct  chemical  union  of  water  with  other  substances. 

Water  assists  as  a  solvent  in  many  chemical  actions. 
Two  solids  may  be  in  contact  with  each  other  and  no  re- 
action take  place.  Yet  a  small  amount  of  water  may  quick- 
ly cause  a  reaction  between  the  two  materials.  Baking 
powder  and  Seidlitz  powders  are  familiar  examples  of  this 
fact.  The  same  statement  holds  true,  moreover,  of  gaseous 
as  well  as  solid  mixtures.  The  presence  of  moisture  seems 
to  be  one  of  the  conditions  essential  to  the  reaction  of  sub- 
stances in  the  gaseous  state.  For  this  reason  solutions  of 
solids  in  water  are  more  frequently  employed  in  chemistry 
than  the  solids  themselves.  Water  is,  therefore,  very  useful 
in  the  chemical  laboratory. 

Water  seems  to  aid  in  another  way  in  bringing  about 
certain  reactions.  The  ordinary  rusting  of  iron  which 
takes  place  under  the  usual  conditions  of  that  action  is  an 
example.  It  is  a  well  known  fact  that,  if  tools,  machinery 
and  other  implements  are  kept  in  a  dry  shed  or  coated  with 
oil  to  keep  off  the  atmospheric  moisture  and  rain,  they  do 
not  rust.  Iron  is  plated  with  tin,  zinc,  or  nickel  for  that 
reason,  to  cover  the  iron  and  prevent  its  rusting.  The 
same  point  is  true  also  of  the  rotting  of  wood.  Under  ordi- 
nary conditions,  wood  cannot  rot  if  dry.  Moisture  aids 
bacteria  in  attacking  wood,  We  paint  our  houses  and  dip 
our  fence  posts  in  tar  or  creosote  or  zinc  chloride  to  keep 
out  water  or  to  impregnate  the  woody  fiber  with  compounds 
that  will  prevent  bacterial  action. 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  39 

When  combined  with  substances  Uke  carbon  dioxide, 
sulphur  dioxide  and  other  atmospheric  gases,  water  be- 
comes a  very  active  agent  in  decomposing  rocks  and  soils. 
This  subject  will  be  more  completely  discussed  in  the 
chapter  upon  soils. 

Usefulness  in  Nature.  Water  in  the  course  of  its  cycle 
has  effected  great  changes  in  the  earth's  surface.  By 
the  mechanical  process  of  erosion  and  transportation  of 
rock  material,  by  the  physical  solution  of  soil  material, 
and  by  chemical  action  upon  soils  and  rocks,  it  has  changed 
the  distribution  of  the  solid  matter  of  the  globe. 

Water  vapor  is  the  most  variable  constituent  of  the 
atmosphere  and  the  most  important  from  a  geological 
point  of  view.  It  not  only  dissolves  and  disintegrates  rocks 
and  soils,  but  it  also  acts  as  a  carrier  for  other  substances, 
distributing  them  and  making  them  more  active.  For 
example,  the  rainfall  dissolves  and  concentrates  other  in- 
gredients of  the  atmosphere  and  brings  them  to  the  ground. 
At  least  two  of  these  substances,  oxygen  and  carbon  dioxide, 
are  of  the  greatest  importance,  since  they  serve  to  bring 
about  in  the  earth's  surface  changes  that  vitally  affect 
all  life  processes.  Without  the  aid  of  water,  their  effective- 
ness would  be  very  small.  Certain  other  constituents  of 
the  air  as  ammonia  gas  and  sulphur  dioxide  are  brought 
to  earth  by  water  vapor.  The  quantities  of  these  gases 
dissolved  and  distributed  are  small  and  variable,  but  they 
affect  plant  life  and  are  important  to  note  in  this  connection. 

As  has  been  already  indicated  the  downward  flow  of  water 
from  the  land  surface  into  rivers  and  oceans  is  a  part  of 
the  great  circulation  of  water.  In  this  manner  water  dis- 
solves from  rocks  and  soils  considerable  mineral  matter  and 
also  carries  much  solid  material  in  suspension.  This  action 
on  the  part  of  water  is  commonly  called  erosion  and  is  ex- 
ceedingly important  in  bringing  about  certain  results. 
Erosion  is  partly  mechanical  and  partly  chemical  and  the 


40  CHEMISTRY  OF   THE  FARM  AND  HOME 

two  actions  re-enforce  each  other.  By  flowing  streams 
rocks  are  ground  to  sand  and  new  surfaces  are  exposed  to 
chemical  attack.  Then  chemical  solution  weakens  the 
rocks  and  renders  them  easier  to  wear  away  mechanically. 
According  to  an  estimate  the  total  annual  rainfall  upon  all 
the  land  of  the  globe  amounts  to  29,347  cubic  miles.  Of 
this,  6,524  cubic  miles  drain  off  through  rivers  to  the  sea. 
A  cubic  mile  of  river  water  weighs  4,205,650,000  tons  approx- 
imately and  carries  in  solution,  on  the  average,  762,587 
tons  of  foreign  matter.  In  all  nearly  five  billion  tons  of 
solid  substances  are  thus  carried  annually  to  the  ocean. 
These  figures  give  some  idea  of  the  extent  of  the  chemical 
work  which  the  percolating  waters  are  doing.  Taking  the 
Mississippi  river  as  an  example,  it  has  been  estimated  that, 
if  all  the  material  which  this  river  carries  in  solution  into  the 
Gulf  of  Mexico  yearly  were  collected  in  one  big  mass,  it 
would  make  a  pile  of  sohd  matter  covering  one  square 
mile  to  a  height  of  ninety  feet.  If  the  sediment  which  is 
carried  in  suspension  were  added  to  this  pile,  it  would  add 
another   241    feet   of   solid   matter. 

Climatic  Effects.  Water  has  powerfully  affected  cli- 
mates. The  gulf  stream  helps  to  make  the  British  Isles 
habitable  for  men.  Without  this  warm  current  their  cli- 
mate would  approximate  that  of  Labrador.  Other  portions 
of  the  globe  are  influenced  in  a  like  manner  by  the  oceanic 
circulation.  On  account  of  the  high  specific  heat  of  water 
large  bodies  of  water  tend  to  equalize  the  temperature  of 
adjacent  land. 

The  atmospheric  circulation  of  water  has  also  an  equaliz- 
ing influence.  The  vast  amount  of  water  changed  to  vapor 
froni  the  surface  of  oceans  in  warm  climates  absorbs  an 
immense  amount  of  heat.  This  heat  is  again  liberated  when 
the  vapor  condenses  to  rain  or  snow  in  colder  regions.  At- 
mospheric vapor,  moreover,  acts  as  a  sort  of  blanket  over 
the  earth's  surface,  helping  to  retain  the  warmth  of  the 


WATER  AA'D  ITS  CONSTITUENT  ELEMENTS  41 

latter.  The  effect  of  fogs,  mists  and  clouds  in  keeping  off 
frosts  during  the  nights  of  late  summer  and  fall  is  an  instance 
of  this  fact.  Tyndall,  the  English  scientist,  has  expressed 
this  point  very  strongly  in  the  following  manner:  "Aqueous 
vapor  is  a  blanket  more  necessary  to  the  vegetable  life  of 
England  than  clothing  is  to  man.  Remove  for  a  single 
night  the  aqueous  vapor  from  the  air  which  overspreads 
this  country,  and  every  plant  capable  of  being  destroyed 
by  a  freeezing  temperature  would  perish.  The  warmth  of 
our  fields  and  gardens  would  pour  itself  unrequited  into 
space,  and  the  sun  would  rise  upon  an  island  held  fast  in  the 
iron  grip  of  frost." 

Relation  of  Water  to  the  Soil.  Water  is  one  of  the  most 
important  factors  concerned  in  the  formation  of  soils  and  the 
changes  that  take  place  in  soils.  Without  water  soils  would 
never  have  been  formed.  A  certain  amount  of  water  is 
necessary  for  the  changes  that  are  vital  to  agriculture. 
Yet,  as  already  pointed  out,  too  much  water  may  cause 
erosion  and  rapid  loss  of  fertility.  The  water  supply  is 
the  factor  in  plant  production  which  is  often  the  least 
controllable,  and,  therefore,  the  most  vital.  For  this  reason 
everything  which  aids  in  any  way  the  absorption  and  reten- 
tion of  water  in  soils  or  which  prevents  undue  loss  of  water 
is  to  be  promoted  to  the  utmost.  The  control  of  soil  moisture 
is  the  subject  of  special  study  in  soil  physics  and  in  so-called 
dry  farming. 

One  important  manner  in  which  water  affects  soil  for- 
mation is  by  the  expansion  of  ice  in  rock  crevices  and  in 
soil  lumps.  By  this  means  large  rocks  are  gradually  broken 
down  into  soil  particles  and  clods  of  earth  into  finer  portions. 
The  great  usefulness  of  this  action  is  seen  in  fall  plowing, 
after  which  nature  with  little  effort  efficiently  pulverizes 
and  cultivates  the  soil. 

Relation  of  Water  to  Plant  Life.  The  importance  of 
this  relation  can  hardly  be  realized.     Water  serves  plants 


42  CHEMISTRY  OF  THE  FARM  AND  HOME 

in  a  number  of  vital  ways.  It  helps  transport  food  from 
the  soil  and  from  one  part  of  the  plant  to  another.  It 
regulates  the  temperature  of  the  plant.  It  maintains  the 
turgidity  of  the  cells  and  gives  form  and  rigidity  to  the 
plant  while  in  active  growth.  It  is  the  most  abundant 
constituent  of  plant  tissues.  It  is  an  important  constituent 
of  the  organic  compounds  produced  by  the  plant  in  its 
growth.  Water,  moreover,  combines  with  some  soil  com- 
pounds, making  them  soluble,  so  that  they  can  be  more 
readily  taken  up  by  plants. 

In  countries  of  Hmited  rainfall,  irrigation  is  necessary 
before  crops  can  be  raised.  It  is  very  important  that  the 
character  of  the  water  be  such  that  it  will  not  injure  the 
plants.  If  the  water  contains  common  salt,  sodium  carbo- 
nate, or  other  soluble  compounds,  these  substances  may 
accumulate  in  the  soil  and  rise  to  the  surface  upon  evap- 
oration, giving  the  effect  commonly  called  alkali.  In  other 
cases,  lowlands  or  lands  adjacent  to  rivers  are  sometimes 
overflowed  with  muddy  water.  In  this  manner  a  sediment 
of  finely  divided  particles  is  formed.  This  is  rich  in  plant 
food  and  enormously  increases  the  fertility  of  lands  sub- 
jected to  that  treatment.  In  certain  localities  lands  are 
systematically  treated  in  this  way.  The  valley  of  the  Nile 
is  a  notable  example. 

Relation  of  Water  to  Animal  Life.  Water  is  as  vital 
to  the  life  of  the  animal  as  it  is  to  plants.  In  a  general  way, 
it  may  be  said  to  perform  somewhat  the  same  functions. 
The  principal  constituent  of  animal  bodies  is  water.  It  is 
necessary  for  the  digestion  process  and  the  transfer  of  the 
important  body  fluids.  It  helps  to  equalize  the  temperature 
of  the  animal  body  with  external  conditions. 

The  question  of  drinking  water  is  one  in  which  we  are 
all  interested.  The  substances  present  in  the  water  may 
or  may  not  affect  its  usefulness  in  this  respect.  Those 
materials  dissolved  out  of  rocks  and  minerals  are  usually 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  43 

not  harmful  to  the  animal  system.  A  certain  amount  of 
such  matter  is  advantageous  since  it  helps  supply  the 
mineral  constituents  of  the  solid  tissues  of  the  body.  But 
a  large  amount  of  dissolved  minerals  may  be  quite  harm- 
ful, the  extent  depending  upon  the  nature  of  the  substances. 
The  presence  of  organic  matter  is  also  to  be  avoided,  be- 
cause it  indicates  possible  contamination  by  sewage.  The 
latter  may  consist  of  the  products  of  animal  life  and  the 
bacteria  which  usually  accompany  such  products.  Some  of 
these  bacteria  may  be  those  which  are  characteristic  of 
certain  contagious  diseases.  In  this  way  typhoid  fever  and 
other  dread  diseases  may  be  spread.  It  is,  therefore,  im- 
portant to  ascertain  the  presence  of  such  organic  compounds 
and  to  purify  the  water  by  suitable  means,  so  that  it  can 
be  safely  used  for  drinking  purposes. 

In  the  Arts.  Water  is  necessary  in  a  large  number  of 
manufacturing  processes  for  cleansing  purposes.  For  ex- 
ample, its  importance  in  connection  with  the  textile  indus- 
tries is  very  great.  The  bleaching  and  dyeing  as  well  as 
cleansing  processes  require  large  quantities  of  water  for 
their  successful  operation.  Water  is  the  most  common 
solvent  used  in  chemical  works. 

One  factor  which  limits  the  use  of  water  in  the  house- 
hold and  in  industry  is  the  so-called  hardness  of  water. 
The  effects  of  hard  waters  are  so  well  known  that  they 
hardly  need  naming.  Every  student  can  tell  the  difference 
between  hard  and  soft  waters  by  their  effect  upon  soap. 
The  curd  or  scum  which  hard  water  forms  with  soap  is  not 
at  all  pleasant  or  desirable  in  laundering  or  industrial 
processes.  It  not  only  interferes  with  the  actual  cleansing 
operation  but  also  adds  to  the  cost.  The  scale  or  sediment 
in  the  bottom  of  a  tea  kettle  or  in  the  tubes  of  a  boiler  is 
another  result  of  the  use  of  hard  waters.  Such  a  residue 
adds  inconvenience  and  increases  the  cost  of  the  operation. 
The  cause  of  the  hardness  of  water  and  the  methods  of 


44       CHEMISTRY  OF  THE  FARM  AND  HOME 

overcoming  this  characteristic  will  be   treated    more  fully 
in  the  discussion  of  calcium. 

OXYGEN 

Introduction.  Oxygen  is  often  called  the  most  import- 
ant element.  It  is  the  most  abundant  element  and  is  very 
active  chemically.  It  is  absolutely  necessary  for  the  pro- 
cesses of  plant  and  animal  respiration  and  of  combustion. 
Among  the  other  changes  caused  by  oxygen  are  the  de- 
cay of  wood  and  other  organic  matter,  the  fermenting  of 
fruit  juices,  and  the  rusting  or  tarnishing  of  metals. 

Distribution.  Oxygen  forms  47%  or  nearly  one  half 
the  weight  of  the  earth's  crust.  It  is  eight  ninths  by  weight 
of  pure  water,  but  only  86%  of  the  ocean.  What  is  the 
cause  of  this  difference?  The  atmosphere  contains  23%  or 
about  one  quarter  by  weight  of  oxygen.  This  element  is 
also  an  important  constituent  of  plant  and  animal  life.  In 
every  one  of  these  cases,  except  the  atmosphere,  the  oxygen 
is  in  the  combined  form.  In  the  atmosphere  it  is  in  the 
free  or  uncombined  form. 

Preparation.  Oxygen  can  be  quite  readily  prepared  in 
a  number  of  different  ways.  Its  liberation  from  water  by 
passing  an  electric  current  through  the  latter  has  been 
shown  already.  Oxygen  may  also  be  prepared  by  liquefy- 
ing the  air  and  allowing  the  liquid  nitrogen  of  the  air  to 
boil  away.     The  liquid  oxygen-  remains  almost  pure.. 

The  most  common  method,  though,  of  preparing  the 
element  is  to  heat  an  oxide*  or  a  peroxide  of  some  metal, 
compound  which  will  readily  surrender  its  oxygen,  potas- 
sium chlorate,  for  example.  By  heating  it  |to  350-400°C. 
oxygen  is  liberated  as  a  gas  and  can  be  collected  over 
water.  When  all  the  oxygen  is  expelled  by  applying  suffi- 
cient heat,  a  white  soUd,  potassium  chloride,  remains  as 
a  non-volatile   residue   in   the  apparatus.     Red    oxide   of 


*  See  note  in  appendix. 


WATER  AND  ITS  CONSTITUENT  ELEMENTS 


45 


mercury,  barium  peroxide,  and  red  lead,  an  oxide  of  lead, 
are  other  compounds  which  give  off  oxygen  upon  being 
heated.  Usually,  however,  a  mixture  of  potassium  chlorate 
and  manganese  dioxide  is  employed.  The  oxygen  is  produced 
from  this  mixture  easily  and  at  a  low  temperature,  about 
200°C.  The  apparatus  which  is  used  for  the  preparation  of 
oxygen  by  this  method  may  be  simple,  as  demonstrated  in 


Figure  12. — The  preparation  of  oxygen. 

Figure  12.  The  mixture  of  four  parts  of  potassium  chlorate 
and  one  part  of  manganese  dioxide  is  placed  in  the  hand 
glass  tube  at  the  left ;  the  latter  is  heated  at  first  carefully, 
then  finally  to  a  high  temperature  to  drive  off  the  oxygen 
through  the  long  glass  tube.  The  gas  is  collected  in  the 
bottle  by  displacement  of  water.  A  number  of  bottles 
may  be  filled  with  water  and  inverted  in  the  pneumatic 
trough  to  be  filled  with  the  oxygen.  It  is  always  best  to 
first  heat  a  small  portion  of  the  mixture  of  potassium 
chlorate  and  manganese  dioxide  in  an  open  test  tube  to 
be  sure  that  there  will  be  no  explosion  in  the  larger  flask. 


46 


CHEMISTRY  OF  THE  FARM  AND  HOME 


It  has  been  found  that,  if  the  potassium  chlorate  is 
heated  to  drive  off  all  the  oxygen  possible,  the  latter  is 
always  39.18%  of  the  weight  of  the  original  substance.  In 
other  words,  there  is  a  definite  proportion  of  oxygen  com- 
bined with  the  potassium  and  chlorine  to  form  potassium 
chlorate.  This  same  phenomenon  is  true  of  every  chemical 
compound  and  the  law  which  is  used  to  express  it  is  called 
the  law  of  definite  proportions.  A  chemical  compound 
always  contains  the  same  elements  in  the  same  proportion 
by  weight. 

There  is  still  another  type  of  reaction  for  generating 
oxygen  from  peroxides,  that  is  by  the  action  of  water  upon 

them.  Figure  13  illus- 
trates the  different  parts 
of  an  autogenor  which 
uses  sodium  peroxide  for 
this  purpose.  The  cakes 
of  fused  peroxide  are 
placed  in  the  inner  cyl- 
inder (1)  and  kept  in 
place  by  the  spring  hold- 
er (10).  The  inside  of 
the  apparatus  (A)  is  then  fitted  into  the  outside  tank  (B) 
which  has  been  previously  nearly  filled  with  water.  The 
complete  apparatus  is  shown  in  (C).  The  oxygen  which  is 
evolved  may  be  passed  through  a  nebuUzer  or  spray  and  is 
used  in  the  medical  profession  and  in  cases  of  first  aid  to 
suffocating  persons.  The  whole  outfit  is  a  convenient  and 
portable  apparatus  for  the  purpose  intended. 

Physical  Properties.  Under  ordinary  conditions  of  pres- 
sure and  temperature,  oxygen  is  a  colorless,  odorless,  and 
tasteless  gas.  It  is  slightly  heavier  than  the  atmosphere, 
one  liter  weighing  1.43  grams  under  standard  conditions. 
The  volume  of  gases  varies  with  temperature  and  pressure; 
the  greater  the  temperature,  with  constant  pressure,  the 


■An  automatic  arrangement  for 
generating  oxygen. 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  47 

greater  the  volume  of  the  gas;  the  greater  the  pressure,  with 
constant  temperature,  the  smaller  the  volume  of  the  gas. 
Evidently,  therefore,  there  must  be  some  standard  condi- 
tions for  comparing  gas  volumes.  Those  commonly  used 
are  0°C.  and  760  m.m.,  the  average  pressure  exerted  by 
the  atmosphere  at  sea  level.  For  a  further  study  of  gas 
volumes  the  student  is  referred  to  textbooks  of  physics. 

Oxygen  may  be  liquefied  by  lowering  the  temperature 
and  increasing  the  pressure.  It  is  then  pale  blue  in  color  and 
boils  at  —  182.5°C.  By  further  cooling,  snow  white  crystals 
of  the  substance  may  be  obtained,  which  melt  at  —  227°C. 
Oxygen  is  only  slightly  soluble  in  water,  about  five  volumes 
being  held  in  solution  in  100  volumes  of  water  at  0°C.  At 
20°C.  only  about  three  volumes  are  soluble,  yet  this  is  suffi- 
cient to  add  desirable  qualities  to  drinking  water  and  fur- 
nish the  oxygen  by  which  fish  and  other  organisms  living  in 
water  are  able  to  sustain  their  life. 

Chemical  Properties.  Oxygen  is  a  very  active  element, 
combining  with  all  the  other  elements  except  fluorine  and 
the  members  of  the  argon  group.  Several  elements,  how- 
ever, will  not  combine  directly  with  oxygen,  but  can  be 
made  to  do  so  by  various  indirect  steps.  This  character- 
istic of  the  general  activity  of  oxygen  distinguishes  it  from 
the  other  elements.  In  some  cases  oxygen  may  form  more 
than  one  compound  with  another  element.  Such  com- 
pounds are  usually  called  oxides.  They  may  be  formed  by 
direct  union  of  the  element  with  oxygen,  either  in  the  air 
under  ordinary  conditions  or  in  pure  oxygen  with  or  with- 
out the  application  of  heat. 

After  a  few  bottles  of  oxygen  have  been  collected,  the 
gas  can  be  tested.  A  square  piece  of  glass  is  placed  over 
the  mouth  of  the  bottle  which  can  then  be  removed  from  the 
trough.  The  bottle  is  inverted  as  shown  in  Figure  14a, 
the  glass  is  moved  to  one  side  and  a  piece  of  smouldering 
charcoal  is  lowered  into  the  oxygen.     Immediately  the  char- 


48 


CHEMISTRY  OF  THE  FARM  AND  HOME 


coal  glows  intensely.  (14b).  Even  fine  iron  wire,  if  heated 
to  the  required  temperature  by  burning  sulphur,  burns  and 
throws  off  red  hot  sparks  of  iron  oxide.  (14c).  In  this  way 
it  can  be  shown  that  substances  which  burn  in  the  air  burn 
much  more  intensely  in  pure  oxygen;  also  that  materials 


^^^  m 


^k 


b  c 

Figure  14. — Testing  oxygen  gas. 

that  oxidize  slowly  in  the  air  do  so  much  more  rapidly  in 
pure  oxygen.  It  can  also  be  proved  that  it  is  the  oxygen  of 
the  air  which  supports  combustion,  and  that  the  other  con- 
stituents of  the  air  retard  it. 

Oxidation.  Such  processes  as  the  above  are  called  oxi- 
dation,  a  more  common  name  being  combustion.  They  are 
usually  attended  by  an  evolution  of  light  and  heat.  Oxida- 
tion may  be  quick  or  slow,  depending  upon  the  material 
oxidized  and  the  conditions  of  the  process.  The  rusting  of 
metals  in  a  moist  atmosphere  is  an  example  of  slow  oxi- 
dation. Other  examples  are  the  decay  of  organic  and  vege- 
table matter  and  the  drying  of  linseed  oil  in  paint  mixtures. 

Heat  must  be  supplied  in  order  to  start  certain  oxida- 
tions. It  may  be  either  the  ordinary  heat  of  the  atmosphere 
or  heat  furnished  artificially.  When  one  portion  of  a  suit- 
able substance  has  been  oxidized,  the  heat  given  off  may  be 
sufficient  to  carry  on  the  oxidation  of  the  other  portions. 
In  some  cases,  however,  the  heat  evolved  is  not  sufficient 
to  maintain  the  process  and  heat  must  be  continually  added 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  49 

from  external  sources  in  order  to  keep  the  process  active. 
Oxidation  may  sometimes  proceed  under  ordinary  atmos- 
pheric conditions.  Heat  is  Uberated  in  small  quantities, 
but  enough  to  gradually  raise  the  temperature  of  the  matter 
concerned.  The  oxidation  is  quickened  by  thi^  process 
until  it  reaches  the  point  where  flame  and  fire  result.  This 
is  frequently  called  spontaneous  combustion.  Instances  of 
this  action  are  seen  where  coal  dust,  sawdust,  thin  films  of 
oil  upon  cotton  waste,  or  wood  saturated  with  oil  have 
been  exposed  to  the  air  for  some  time.  The  material  slowly 
oxidizes,  the  heat  afforded  by  the  oxidation  raises  the  tem- 
perature of  the  mass,  and,  ultimately,  if  the  process  is  allowed 
to  proceed,  a  fire  may  result. 

Frequently  the  process  of  combustion  is  forced,  as,  for 
example,  in  the  boilers  of  engines  and  in  blast  furnaces. 
Air  or  oxygen  is  forced  under  pressure  into  the  furnace. 
This  not  only  furnishes  fresh  portions  of  oxygen  to  hasten 
the  burning  of  the  fuel,  but  also  sweeps  away  the  products  of 
combustion  which  retard  it.  The  same  principle  is  seen  also 
in  heating  stoves  and  furnaces.  By  increasing  the  draught, 
combustion  is  quickened  and  more  heat  is  liberated. 

The  term  deflagration  is  applied  to  an  oxidation  of  a  special 
type.  The  combination  of  the  combustible  substances 
and  the  oxidizing  agent  takes  place  almost  instantaneously 
through  the  whole  mixture.  Gunpowder  is  an  example 
of  a  substance  that  deflagrates  when  ignited  in  the  open  air. 

Kindling  Temperature.  The  temperature  at  which 
a  combustible  substance  begins  to  burn  is  called  its  kindling^ 
or  ignition,  temperature.  This  point  varies  considerably 
with  the  nature  of  the  substance.  Some  materials,  such 
as  gasoline,  will  ignite  at  a  point  only  slightly  above  the 
temperature  of  the  air.  Others  such  as  hard  coal,  require 
a  very  high  temperature  before  they  are  oxidized.  In  prac- 
tice it  is  necessary  to  use  some  substance  which  ignites  at 
a  relatively  low  temperature  in  order  to  cause  other  sub- 


50       CHEMISTRY  OF  THE  FARM  AND  HOME 

stances  to  burn.  Common  examples  of  this  application 
are  seen  in  the  case  of  the  match  and  the  building  of  a  fire 
in  a  stove  or  furnace.  In  the  first  case  the  head  of  the 
match  which  has  been  prepared  from  a  mixture  of  chemicals, 
is  ignited  by  heat  generated  by  simple  friction.  The  heat 
produced  from  the  intense  chemical  reaction  raises  the 
temperature  of  the  wood  to  the  point  at  which  it  in  turn 
ignites.  In  the  stove  fire,  we  use  first  a  layer  of  paper, 
then  of  wood,  then  of  coal.  By  lighting  the  paper,  which 
burns  at  a  very  low  temperature,  heat  is  generated  to  ignite 
the  wood,  and  this  in  turn  produces  heat  to  cause  the  coal 
to  ignite;  whereas  it  would  have  been  simply  impossible 
to  ignite  the  coal  with  the  match  used  in  the  first  instance. 

It  is  possible  to  extinguish  a  fire  by  lowering  the  temper- 
ature below  the  kindling  point.  If  we  blow  out  a  match  we 
have  simply  lowered  the  temperature  of  the  wood  below  the 
point  at  which  it  burns.  An  interesting  application  of  this 
principle  is  the  safety  lamp  which  is  used  by  miners  to  pre- 
vent explosions  of  gases  in  mines.  The  lamp  is  an  ordinary 
lantern  surrounded  by  wire  gauze.  When  it  is  brought  into 
an  explosive  gaseous  mixture,  the  gases  diffuse  through  the 
wire  gauze,  and  burn  inside  the  lamp,  but  the  heat  produced 
is  carried  away  by  the  gauze,  so  that  the  gases  outside  the 
lamp  do  not  reach  the  ignition  temperature.  The  small 
explosions  inside  the  lamp  warn  the  miner  of  his  danger 
and  he  can  escape^from  the  mine  before  any  accident  happens. 

Uses  of  Oxygen.  Oxygen  performs  two  functions  of 
great  importance  to  mankind.  First,  it  is  a  supporter  of 
combustion.  Combustion  may  be  either  the  active  process 
by  which  heat  and  light  are  evolved,  or  certain  slow  proces- 
ses of  animal  and  vegetable  matter  by  which  little  heat  is 
liberated,  such  as  decay  and  fermentation.  The  rusting  of 
metals  might  also  be  included  under  this  head. 

Second,  oxygen  is  a  supporter  of  animal  respiration. 
This  is  really  a  slow  combustion  in  all  parts  of  the  body  to 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  51 

which  the  oxygen  is  carried.  In  this  manner,  heat  is  pro- 
duced and  energy  afforded  to  the  animal  to  carry  out  the 
different  functions  of  the  body.  Oxygen  is  especially  fitted 
for  this  function  for  several  reasons.  It  is  so  abundant  in 
the  atmosphere.  It  is  soluble  in  water,  thus  aiding  fish 
life.  It  does  not  irritate  the  lungs.  The  products  of 
animal  respiration,  water  and  carbon  dioxide,  are  not  cor- 

irosive  to  animal  tissue.  The 
volume  of  oxygen  consumed 
and  that  of  the  carbon  di- 
oxide produced  are  the  same 
and,  therefore,  no  pressure 
is  exerted  either  way.  The 
effect  upon  animals  of  re- 
moving the  oxygen  of  the  air 
is  to  cause  suffocation  and 
death,  while  increase  in  the 
percentage  of  oxygen  leads  to 
J  increased   activities  within 

^^        «  certain  limits.     The  effect  of 

^H        1  pure   oxygen    upon   animals 

^H  ^B  ^L  would  be  that  of  a  poison, 
^H  ^M  ^M  producing  intense  infiamma- 
^H  ^H  Wm  tion,  convulsions,  and  death. 
^H  ^H  ^H  On  the  other  hand,  one  can 
^^      ^^      ^^    breathe   pure    oxygen   for  a 

Figure  l^-I-'Jp^^^^d-^^^^^     storing      ^-^^    ^j^j^^^^    ^^^     ^^^^^^    -^ 

fact  the  gas  is  frequently  ad- 
ministered to  persons  who  are  ill  and  who  experience  difficulty 
in  breathing.  Helmets  equipped  with  oxygen  attachments 
enable  the  diver  to  descend  to  ocean  depths,  the  aviator 
to  ascend  into  rarified  air,  the  fireman  to  stand  in  dense 
smoke,  and  rescuers  to  descend  into  gas-filled  mines. 

Oxygen  is  moreover  an  article  of  commerce  and  is  largely 
used  in  various  industries.     It  may  be  generated  locally 


52  CHEMISTRY  OF  THE-  FARM  A:SW  HOME 

and  used  directly  for  the  purpose  intended,  or  ^t  may  be 
stored  under  pressure  in  wrought  iron  cyHnders  (such  as 
shown  in  Figure  15)  and  thus  shipped  wherever  it  may  be 
required.  Mention  should  be  made  of  the  appHcation 
of  the  oxy-acetylene  and  oxy-hydrogen  processes  in  the 
industries. 

OZONE 

Preparation.  Ozone  may  be  prepared  from  oxygen  or 
air  by  passing  electric  sparks  through  these  gases.  In  this 
manner  a  small  amount  of  the  oxygen  is  converted  to  ozone. 
There  are  certain  chemical  methods  also  of  preparing  the 
substance,  for  example,  if  some  pieces  of  phosphorus  are 
placed  in  a  bottle  and  partially  covered  with  water,  the 
presence  of  ozone  may  soon  be  detected. 

Properties.  Ozone  is  a  colorless  gas  having  the  char- 
acteristic odor  which  is  noticeable  about  electrical  ma- 
chines when  they  are  in  operation.  It  may  be  liquefied 
and  is  then  blue  in  color  and  boils  at  —  119°C. 

Chemically,  ozone  is  similar  to  oxygen  but  is  much  more 
active.  It  is  very  explosive  and  is  converted  into  oxygen 
with  the  liberation  of  heat.  On  account  of  its  activity 
and  oxidizing  properties  ozone  is  used  in  certain  manufactur- 
ing processes  and  for  purifying  water  and  air. 

Relation  ot  Oxygen  and  Ozone.  When  oxygen  is  con- 
verted into  ozone  there  is  a  change  of  volume,  three  volumes 
of  oxygen  forming  two  volumes  of  ozone.  If  this  ozone  is 
then  heated  to  about  300°C.  the  reverse  change  occurs,  two 
volumes  of  ozone  being  changed  to  three  volumes  of  oxygen. 
In  this  phenomenon  no  other  kind  of  matter  is  involved. 
But  there  is  to  be  considered  the  question  of  energy.  It 
may  be  proved  in  a  number  of  ways  that  oxygen  and  ozone 
contain  different  amounts  of  energy;  for  example,  by  the 
fact  that  heat  is  liberated  when  ozone  reverts  to  oxygen. 
The  passage  of  the  electric  sparks  through  the  oxygen 
has  in  some  way  changed  the  amount  of  energy  of  this  sub- 


WATEk  AND  ITS  CONSTITUENT  ELEMENTS  5S 

stance  and  it  has  acquired  new  properties.  Oxygen  and 
ozone  are,  therefore,  the  same  kind  of  matter,  but  have 
different  energy  contents.  When  an  element  exists  in  dif- 
ferent forms,  such  as  the  example  just  cited,  these  are 
called  allotropic  states  or  forms  of  the  element.  There  are 
a  number  of  other  elements  which  possess  this  property  of 

allotropism. 

HYDROGEN 

Introduction.  Hydrogen  is  a  gas  and  the  lightest  sub- 
stance known.  It  is  found  in  a  large  number  of  substances, 
but  is  not  of  very  great  importance  as  an  element.  Hydrogen 
is  most  useful  in  its  combined  forms,  such  as  water  and  the 
organic  compounds  of  plant  and  animal  life.  With  few 
exceptions  it  is  not  a  very  active  element. 

Distribution.  In  the  free  form  hydrogen  has  been  proved 
to  exist  in  enormous  quantities  in  the  atmosphere  of  the 
sun.  It  does  not  occur  in  very  great  quantity  in  the  earth, 
though  it  is  sometimes  found  in  the  atmosphere  near  large 
cities  and  volcanoes.  In  the  combined  form  hydrogen 
exists  in  a  great  many  natural  and  artificial  substances. 
One  ninth  of  the  weight  of  water  is  hydrogen.  Vegetable 
and  animal  matter  contain  this  element.  Fuels,  such  as 
petroleum,  coal,  illuminating  and  heating  gases,  and  wood 
all  contain  hydrogen.  It  is  also  a  constituent  of  all  acids 
and  bases  and  is  found,  moreover,  in  a  large  number  of 
chemical  compounds,  as  ammonia  and  hydrogen  sulphide. 

Preparation.  Hydrogen  may  be  prepared  in  a  number 
of  different  ways  for  experimental  purposes.  Since  it  does 
not  occur  free  in  nature,  it  must  be  secured  from  some  of 
its  compounds.  The  simplest  compounds  containing  this 
element  and  those  which  most  easily  liberate  it  are  water  and 
the  common  acids.  Some  means,  therefore,  of  decomposing 
water  or  the  acids  is  utilized  for  preparing  the  element. 

The  most  convenient  method  is  the  reaction  between 
metals  and   dilute   acids,   simple   contact   under  ordinary 


54 


CHEMISTRY  OF  THE  FARM  AND  HOME 


conditions  being  the  essential  qualifications.  Zinc  and 
iron  are  the  metals  usually  employed,  and  hydrochloric 
acid  and  sulphuric  acid  the  acids. 

In  Figure  16  is  shown  a  simple  apparatus  for  generating 
hydrogen.  The  acid  is  poured  through  the  thistle  tube  B 
into  the  flask  A  which  contains  the  metal.  The  hydrogen 
is  at  once  liberated  as  a  gas  and  passes  off  through  the 


Figure  16. — The  preparation  of  hydrogen. 

tube  C.  It  may  be  collected  in  bottles  over  water  as  in 
the  preparation  of  oxygen.  As  considerable  heat  is  evolved 
by  the  process,  there  is  no  need  of  heating  the  flask,  in  fact 
no  flame  should  be  near  a  hydrogen  generator. 

Water  serves  as  a  convenient  material  for  preparing 
hydrogen,  since  it  is  the  most  common  compound  of  the 
element.  It  will  be  recalled  that  hydrogen  is  one  of  the 
two  substances  given  off  by  the  electrolysis  of  water.  Metals 
also  were  shown  to  have  an  effect  upon  water  and  to  liberate 
hydrogen.  Though  there  is  a  number  of  metals  which  do 
this,  sodium  and  potassium  are  the  ones  which  are  most 
commonly  used  for  experimental  purposes.  Figure  17 
shows  the  reaction  of  a  piece  of  sodium  upon  water.     A 


WATER  AND  ITS  CONSTITUENT  ELEMENTS 


55 


lead-sodium  alloy  is  also  used  for  this  reaction.  If  steam 
is  passed  over  red  hot  iron,  hydrogen  is  liberated  and  may 
be  collected;  iron  oxide  is  the  other  product. 

Physical  Properties.  Hydrogen  is  a  colorless,  odorless, 
and  tasteless  gas.  It  is  the  lightest  substance  known.  One 
liter  of  hydrogen  at  0°C.  and  760  m.m.  weighs  only  0.0896 
gram.  Comparing  equal  volumes,  air  is  14.4  times,  oxygen 
is  16  times,  and  water  is  11,000  times  heavier  than  hydrogen. 

m 


m 


Figure  17. — Experiments  with  hydrogen. 

It  is  not  very  soluble  in  water,  being  about  half  as  soluble 
as  oxygen.  Hydrogen  is,  however,  absorbed  by  several 
metals,  especially  palladium,  a  process  which  is  called 
occlusion.  Enough  heat  is  developed  by  this  action  to 
ignite  the  gas.  Hydrogen  also  illustrates  the  phenomenon 
of  diffusion.  It  readily  passes  through  porous  substances 
and  mixes  with  other  gases.  Figure  17  shows  a  tube 
which  has  a  plaster  of  Paris  cap  at  one  end.  After  the  tube 
is  filled  with  hydrogen  and  inserted  in  water,  the  gas  passes 
out  through  the  plaster  cap  faster  than  the  air  can  enter. 
Water  rushes  in  and  takes  the  place  of  the  hydrogen  lost  in 
this  way.  Since  the  rate  of  diffusion  of  a  gas  is  inversely 
proportional  to  the  square  root  of  its  density,  hydrogen 
diffuses  more  rapidly  than  any  other  substance.     By  lower- 


56       CHEMISTRY  OF  THE  FARM  AND  HOME 

ing  the  temperature  and  increasing  the  pressure  hydrogen 
may  be  liquefied  and  even  solidified.  It  conducts  heat 
and  electricity  better  than  any  other  gas. 

Chemical  Properties.  Hydrogen  burns,  but  does  not 
support  combustion.  With  oxygen,  either  pure  or  from  the 
air,  it  forms  water.  This  reaction  may  be  induced  by 
thrusting  a  lighted  taper  into  a  mixture  of  oxygen  and 
hydrogen  or  by  passing  an  electric  spark  through  the  mix- 
ture. The  two  gases  unite  so  violently  that  an  explosion 
may  result,  hence  care  should  be  used  in  testing  hydrogen. 
With  chlorine  hydrogen  forms  hydrochloric  acid,  a  reaction 
which  may  be  effected  in  a  manner  similar  to  the  union  of 
oxygen  and  hydrogen.  With  a  number  of  other  elements 
hydrogen  unites  to  give  corresponding  hydrogen  compounds. 
With  these  exceptions  hydrogen  is  a  comparatively  inert 
material  at  ordinary  temperatures.  Figure  17  illustrates 
a  characteristic  experiment  with  hydrogen.  A  bottle  con- 
taining the  element  is  inverted  and  a  burning  stick  thrust 
up  into  the  gas.  The  Hghted  stick  is  at  once  extinguished, 
but  the  hydrogen  catches  fire  and  burns  at  the  mouth  of 
the  bottle  with  an  almost  invisible  but  very  hot  flame. 

The  reaction  of  hydrogen  and  oxygen  is  very  characteristic 
of  these  two  elements.  Hydrogen  will  react  with  free  oxygen 
or  combined  oxygen.  In  other  words,  it  will  abstract  oxygen 
from  its  combination  with  other  elements.  This  process  is, 
therefore,  the  reverse  of  adding  oxygen  to  an  element. 
The  term  reduction  is  applied  to  the  removal  of  oxygen  from 
a  substance.  What  is  the  term  applied  to  the  addition  of 
oxygen?  Reduction  processes  are  of  great  industrial  im- 
portance, since  many  metals  are  abstracted  from  their  ores 
in  this  manner.  As  will  be  discussed  later,  other  substances, 
as  carbon  and  aluminium,  are  used,  as  well  as  hydrogen, 
to  effect  reduction. 

Usefulness.  In  the  free  form  hydrogen  has  a  few  uses, 
as  a  reagent  for  laboratory  purposes,  a  reducing  agent  in 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  57 

metallurgical  processes  and  a  material  for  filling  balloons, 
especially  those  that  are  to  travel  some  distance.  Hydrogen 
is  also  a  constituent  of  water  gas,  producer  gas,  and  artificial 
and  natural  illuminating  gases  which  are  valuable  for  their 
commercial  purposes.  Advantage  is  taken  of  the  large 
amount  of  heat  produced  by  the  combination  of  hydrogen 
with  oxygen  in  the  oxy-hydrogen  blowpipe.  By  directing 
the  flame  from  this  burner  against  a  piece  of  lime  or  other 
substance  which  is  difficult  to  melt,  the  lime  becomes  in- 
tensely bright.  It  is  called  the  lime,  calcium,  or  Drum- 
mond  light,  and  is  employed  in  operating  the  stereopticon. 
In  the  combined  form  hydrogen  is  of  great  importance 
in  its  different  compounds,  such  as  water,  acids,  and  the 
compounds  of  plant  and  animal  life.  The  applications  of 
hydrogen  in  these  connections  may  be  inferred  from  the 
discussion  of  those  substances. 

HYDROGEN  PEROXIDE 

Introduction.  Besides  water  there  is  another  compound 
of  hydrogen  and  oxygen  which  contains  twice  as  much  oxy- 
gen in  proportion  to  the  hydrogen  as  water.  This  substance 
is  commonly  called  hydrogen  dioxide  or  hydrogen  peroxide. 

Preparation.  Hydrogen  peroxide  is  usually  prepared  by 
the  action  of  dilute  sulphuric  acid  on  barium  peroxide. 
The  dilute  solution  of  the  hydrogen  peroxide  thus  formed 
may  be  concentrated  by  carefully  distilling  off  the  water. 

Properties.  Hydrogen  peroxide,  when  pure,  is  a  color- 
less syrupy  liquid  with  a  specific  gravity  of  1.49.  It  is 
easily  decomposed  into  water  and  oxygen,  this  being  its 
most  characteristic  property.  If  prepared  in  the  form  of  a 
dilute  solution,  it  is  then  quite  stable,  though  it  should  be 
kept  in  a  dark  cool  place,  since  both  light  and  heat  aid  in 
its  decomposition. 

Uses.  In  the  form  of  a  3%  solution,  peroxide  of  hydro- 
gen is  a  common  preparation  to  be  secured  from  druggists. 


58  CHEMISTRY  OF  THE  FARM  AND  HOME 

It  is  used  in  medicine  and  in  the  household  as  an  antiseptic. 
This  usefulness,  as  well  as  the  other  commercial  purposes 
for  which  it  is  employed,  depends  upon  the  strong  oxidizing 
properties  of  the  compound. 

THE  RELATION  OF  WATER,  HYDROGEN,  AND  OXYGEN 

The  student  has  now  become  familiar  with  the  fact  that 
water  is  a  compound  which  can  be  decomposed  into  two 
elements,  hydrogen  and  oxygen.  He  has  also  studied  the 
properties  of  all  three  of  these  substances.  There  has  un- 
doubtedly come  to  his  mind  these  questions,  in  regard  to 
them.  What  is  the  weight  of  the  gases  hydrogen  and 
oxygen,  which  can  be  secured  from  a  given  amount  of  water? 
How  can  this  gravimetric  relation  be  proved? 

The  composition  of  a  compound  is  determined  by 
analysis  and  synthesis,  which  mean  taking  apart  and  putting 
together.  As  far  as  possible,  it  is  better  to  use  both  these 
methods,  as  they  strengthen  each  other  in  reaching  a  final 
conclusion.  Both  analysis  and  synthesis  can  be  qtialita- 
tive  or  quantitative.  These  names  practically  suggest  their 
meaning;  qualitative,  the  quality  or  kind,  and  quantitative, 
the  amount  of  substances  involved.  In  other  words,  a 
qualitative  study  asks.  What  does  the  substance  contain?  and 
a  quantitative  study.  How  much  does  the  substance  contain? 

The  composition  of  water  is  an  excellent  subject  for 
applying  the  methods  of  analysis  and  synthesis.  A  special 
form  of  analysis,  electrolysis,  and  two  other  methods,  the 
action  of  metals  and  of  chlorine,  have  been  studied  in  a 
qualitative  manner.  Let  us  now  turn  to  the  question  of 
the  quantitative  composition  of  water.  It  has  already  been 
stated  that  from  the  electrolysis  of  water  only  hydrogen 
and  oxygen  are  produced  and  that  their  ratio  by  volume 
is  two  to  one.  The  complete  proof,  however,  that  these 
two  gases  are  united  in  the  same  proportion  in  water  follows 
from  the  volumetric  synthesis  of  water.     Figure  18  shows 


WATER  AND  ITS  CONSTITUENT  ELEMENTS 


59 


SpaLTk 
Coil 


the  apparatus  which  is  used  to  demonstrate  this  experiment. 
A  tube  closed  at  one  end,  a  eudiometer,  is  filled  with  mercury. 
Two  volumes  of  hydrogen  and  one  volume  of  oxygen  are 
passed  into  the  tube  and  displace  part  of  the  mercury;  by 
raising  or  lowering  the  leveling  tube  on  the  right  it  is  pos- 
sible to  get  the  volume  of  the  gases  at  atmospheric  pressure. 
The  tube  containing  the  gases  is  now  surrounded  by  a 

steam  jacket  and  steam  is  passed 
through  until  the  volume  of  the 
gases  becomes  constant.  An  elec- 
tric spark  is  sent  through  the  mix- 
ture in  the  inner  tube  and  the 
union  of  the  hydrogen  and  oxygen 
thus  effected.  The  steam  is  again 
passed  through  the  jacket  and  the 
volume  of  the  gases  read  a  second 
time.  The  volume  is  now  only 
two  thirds  as  great  as  that  of  the 
original  gases.  The  substance  is 
in  the  form  of  steam,  since  the 
purpose  of  the  outer  steam  jacket 
is  to  compare  the  volumes  of  all 
the  gases  at  the  same  tempera- 
ture. .  In  this  way  it  can  be  proved  that  two  volumes  of 
hydrogen  and  one  volume  of  oxygen  unite  to  form  two  volumes 
of  water  vapor.  The  experiment  proves  that  the  proportion 
by  volume  in  which  hydrogen  and  oxygen  combine  in  the 
production  of  water  is  the  same  as  that  in  which  these  gases 
are  obtained  from  water.  It  can  also  be  shown  that  the 
sum  of  the  weights  of  hydrogen  and  oxygen  equals  the 
weight  of  the  water  produced. 

It  is  now  necessary  to  know  the  proportion  by  weight  in 
which  hydrogen  and  oxygen  are  combined  in  water.  Figure 
19  shows  the  apparatus  which  can  be  used  to  ascertain  this. 
A  known  weight  of  copper  oxide  is  placed  in  the  tube  D. 


StefiLia 


Figure  18. — The  volumetric  syn 
theaia  of  water. 


60  CHEMISTRY  OF  THE  FARM  AND  HOME 

While  this  is  heated,  a  current  of  pure  hydrogen  is  passed 
over  it.  The  hydrogen  unites  with  the  oxygen  of  the  cop- 
per oxide  and  forms  water,  leaving  the  copper  behind  in 
the  tube.  The  water  is  absorbed  in  the  tube  E  and  its 
weight  determined.  The  weight  of  the  remaining  copper 
can  also  be  secured.  Since  the  loss  of  the  weight  of  the 
copper  oxide  is  oxygen  and  the  gain  in  the  weight  of  the 


H  — 


D 


Figure  19. — The  gravimetric  synthesis  of  water. 

U-tube  E  is  water,  the  difference  between  these  two  weights 
is  hydrogen.  Hence  it  is  a  simple  matter  to  establish  the 
quantitative  relation  of  these  three  substances.  The  result 
of  many  such  experiments  has  proved  the  relation  to  be  as 
follows : 

Oxygen  Hydrogen  Water 

8  parts  1  part  9  parts 

For  reasons  which  will  be  given  later,  it  is  more  con- 
venient to  state  the  composition  of  water  by  weight  .as  16 
parts  of  oxygen  to  2  parts  of  hydrogen. 

If  the  student  now  compares  the  weights  of  equal  vol- 
umes of  hydrogen  and  oxygen  (see  physical  properties),  he 
will  find  that  oxygen  is  sixteen  times  heavier  than  hydrogen. 
The  one  volume  of  oxygen  produced  from  the  electrolysis 
of  water,  therefore,  must  be  eight  times  heavier  than  the  two 
volumes  of  hydrogen.  But  this  is  the  ratio  actually  found  in 
determining  the  gravimetric  composition  of  water.  Hence, 
the  composition  of  water  is  said  to  be  (1)  by  weighty  one  part 
hydrogen  and  eight  parts  oxygen,  and  (2)  by  volume,  two  parts 
hydrogen  and  one  part  oxygen. 


Water  and  its  constituent  elements         61 

ATOMS,  MOLECULES,  ATOMIC  WEIGHTS 

Molecules.  According  to  the  atomic  theory  all  sub- 
stances are  made  up  of  minute  particles,  called  molecules. 
These  are  the  smallest  particle  of  an  element  or  a  compound 
which  is  capable  of  existing  alone  and  retaining  most  of  the 
properties  of  the  mass  of  the  original  substance.  The 
molecules  of  a  pure  substance  are  exactly  alike,  but  different 
from  those  of  every  other  substance.  One  difference  is 
their  mass,  or  weight. 

Atoms.  The  molecules  of  a  substance  are  composed  of 
particles  of  the  elements  which  constitute  it.  If  the  sub- 
stance is  an  element,  the  particles  are  all  alike;  if  the  sub- 
stance is  a  compound,  there  may  be  several  different  kinds 
of  particles.  Such  particles  are  called  atoms.  Molecules, 
then,  are  groups  of  atoms  held  together  hy  chemical  attraction. 

An  atom  is  the  smallest  particle  of  a  substance.  It 
does  not  exist  alone  but  is  always  combined  with  other 
atoms  to  form  molecules.  There  are  as  many  kinds  of  atoms 
as  of  elements.  They  are  extremely  small,  indivisible  and 
unchangeable  by  any  physical  or  chemical  means.  They 
exhibit  an  attractive  force  for  other  atoms  which  varies  under 
different  conditions  and  with  the  different  elements. 

Atomic  Weights.  If  the  molecules  have  weight,  then 
the  atoms  composing  them  also  have  weight.  It  has  been 
possible  by  experimenting  and  reasoning  to  assign  to  the 
different  atoms  relative  weights.  Since  hydrogen  is  the 
lightest  substance  known,  it  may  be  concluded  that  it  has 
the  lightest  atom.  For  the  sake  of  convenience,  therefore, 
the  atomic  weight  of  hydrogen  can  be  taken  as  unity,  or 
1.0,  and  used  as  a  standard  for  other  atomic  weights.  Oxy- 
gen is  nearly  16  times  as  heavy  as  hydrogen,  the  actual 
ratio  is  15.87.  For  several  reasons  it  is  now  preferred  to 
use  the  atomic  weight  of  oxygen  as  the  standard  with  a 
value  of  16,  in  which  case  the  atomic  weight  of  hydrogen 
becomes  1.008.     One  cause  for  this  preference  is  the  fact 


e^       CHEMISTRY  OF  THE  FARM  AND  HOME 

that  oxygen  combines  with  practically  all  the  other  elements. 
What  advantage  has  that  feature  over  the  use  of  hydrogen 
as  the  standard?  A  complete  list  of  atomic  weights  appears 
in  the  appendix  in  the  table  of  elements.  The  student 
should  appreciate  the  fact  that  these  atomic  weights  are  only 
relative,  that  is,  comparative  to  some  standard,  since  the 
atomic  masses  are  too  small  to  be  weighed  absolutely. 

SYMBOLS,  FORMULAS,  EQUATIONS 

Sjnnbols.  It  is  desirable  as  far  as  possible  to  simplify 
the  manner  of  expressing  chemical  reactions.  We  may 
assign  to  each  element  a  certain  letter  or  group  of  letters, 
called  a  symbol.  The  letter  chosen  is  usually  the  initial 
one  in  the  name  of  the  element  or  a  second  letter  in  addition 
to  the  first,  when  there  are  two  or  more  elements  beginning 
with  the  same  initial.  For  example,  C  stands  for  carbon, 
CI  for  chlorine,  Co  for  cobalt,  and  Cu  for  copper.  The 
Latin  name  for  copper  is  cuprum,  hence  the  symbol  Cu. 
The  student  will  gradually  become  familiar  with  these  and 
other  symbols  and  appreciate  their  convenience  as  short- 
hand expressions  for  chemical  names. 

Formulas.  A  compound  is  composed  of  two  or  more 
elements;  hence  there  will  be  in  the  abbreviated  expression, 
called  formula,  for  these  compounds  two  or  more  symbols 
depending  upon  the  kind  of  elements  present  and  their 
amount.  Formulas  are  more  difficult  to  learn  and  will  be 
studied  in  connection  with  their  respective  compounds. 

Equations.  If  we  wish  to  express  a  chemical  reaction, 
we  may  do  so  by  grouping  the  symbols  or  formulas  of  the 
substances  taking  part  in  the  reaction  into  an  equation. 
The  materials  at  the  beginning  of  the  reaction  are  placed 
on  the  left-hand  side  of  the  equation  and  are  known  as 
factors.  Those  substances  formed  by  the  reaction  are 
placed  on  the  right-hand  side  and  are  called  products. 
Instead  of  the  usual  sign  of  equality,  however,  an  arrow 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  63 

is  placed  between  the  halves  as  — >.  Sometimes  a  reaction 
may  be  reversed  and  proceed  in  two  ways  at  the  same  time, 
when  the  double  arrow  ^  is  used.  An  equation,  therefore, 
is  merely  a  convenient  method  of  expressing  a  chemical 
reaction  by  using  the  formulas  of  the  reacting  materials. 
It  should  be  kept  in  mind  that  equations  are  the  results 
of  experiments.  When  it  is  known  what  substances  take 
part  in  a  reaction,  then  it  is  possible  to  write  the  equation 
for  that  reaction.  Not  only  are  th^  actual  kinds  of  matter 
involved  indicated  in  equations,  but  the  latter  have  a  quan- 
titative meaning  as  well.  The  proportions  by  weight  of  the 
reacting  substances  and  of  the  products,  and  further,  when 
gases  are  concerned,  the  proportions  by  volume,  may  all  be 
shown  in  equations.  The  student  should  not  place  the 
learning  of  the  equation  above  the  fact  represented  by  the 
equation.  As  he  becomes  familiar  with  chemical  reactions, 
he  will  become  accustomed  to  the  use  of  equations.  The 
fact  is  the  important  thing  to  learn;  the  equation  is  second. 
It  might  be  well  to  apply  the  points  just  under  discussion 
to  a  few  reactions  which  have  been  already  studied.  Take 
for  example  the  electrolysis  of  water. 

ttr}  -^  Hydrogen  and  Oxygen 

Water  By 

Electrolysis 
2H2O  ->  2H2+O2 

The  formula  for  water  is  H2O.  Two  molecules  are  taken 
in  the  equation  to  represent  the  fact  that  two  molecules 
of  hydrogen  are  formed  and  one  molecule  of  oxygen.  It 
will  be  recalled  that  this  is  in  accordance  with  the  fact  that 
two  volumes  of  hydrogen  and  one  volume  of  oxygen  are 
liberated  by  the  electrolysis  of  water;  also  that  the  mole- 
cule of  these  two  elements  is  composed  of  two  atoms.  If 
the  equation  factors  were  divided  by  two,  only  one  atom 
of  oxygen  would  appear.  This  would  not  be  in  harmony 
with  the  view  that  the  molecule  is  the  smallest  part  of  a 


64  CHEMISTRY  OF  THE  FARM  AND  HOME 

substance  that  can  exist  alone  and  retain  the  properties 

of  the  original  material.     For  this  reason  and  others  it  is 

preferable  to  write  equations  in  the  molecular  form  instead 

of  the  atomic  form.     The  proportions  by   weight  are  also 

shown  to  be  that  18  parts  of  water  give  2  parts  of  hydrogen 

and  16  parts  of  oxygen. 

Another  example  of  an  equation  is  the  action  of  sodium 

upon  water: 

TT,,j_„„„„l  f  Sodium 

qJ^^°|^"  and  Sodium  -^         Hydrogen  and  Hydrogen 
J  lOxygen 

Water  Sodium  hydroxide 

2H2O     +     Na2         -^         H2     +     2NaOH 

This  equation  represents  the  fact  that  two  molecules  of 
water  react  with  a  molecule  of  sodium  to  form  a  molecule  of 
hydrogen  and  two  of  sodium  hydroxide.  It  is  evident  that 
only  half  of  the  hydrogen  of  water  is  replaced  by  sodium 
in  this  action.  The  other  portion  of  hydrogen  is  combined 
with  sodium  and  oxygen  to  form  sodium  hydroxide,  or 
caustic  soda. 

In  the  preparation  of  oxygen  by  heating  potassium 
chlorate  two  molecules  of  potassium  chlorate  are  changed 
into  three  molecules  of  oxygen  and  two  of  potassium  chloride. 
The  equation  is 

2  KCIO3  (heated)     ->     3  O2     +2KC1. 

In  other  words  by  heating  two  molecular  weights  of  potas- 
sium chlorate,  three  molecular  weights  of  oxygen  are  pro- 
duced. Further  examples  of  equations  will  appear  in  con- 
nection with  their  reactions. 

SUMMARY 

Water  is  probably  the  most  famihar  example  of  a  chemical  com- 
pound. Its  importance  is  shown  by  the  facts  that  it  is  partly  responsible 
for  the  present  appearance  of  the  earth's  surface,  that  it  is  absolutely 
necessary  for  plant  and  animal  life,  that  it  affects  climatic  con- 
ditions and  that  it  is  a  necessity  in  commerce  and  industry.     Water 


WATER  AND  ITS  CONSTITUENT  ELEMENTS  65 

is  very  widely  distributed  not  only  as  bodies  of  free  water  but  also  in 
close  association  with  the  vegetable,  animal,  and  mineral  kingdoms. 
There  are  many  different  kinds  of  natural  waters,  all  of  which  are  more 
or  less  closely  related  in  a  constant  circulation.  These  natural  forms 
are  not  pure,  since  there  are  many  foreign  materials  dissolved  by  water 
in  its  cycle.     Water  may,  however,  be  purified  by  distillation. 

The  physical  properties  of  water  make  it  of  the  utmost  value  to 
man.  It  is  the  most  famihar  illustration  of  a  substance  that  can 
exist  in  three  states"  of  matter  without  change  of  composition.  As 
a  liquid,  its  solvent  properties  are  important;  as  a  gas,  steam,  it  is 
of  untold  value  for  industrial  purposes;  as  a  sohd,  ice,  it  causes  many 
changes  of  importance  in  nature. 

Water  is  a  compound  of  oxygen  and  hydrogen.  This  may  be 
proved  by  decomposing  it  by  electrolysis,  by  the  action  of  metals, 
and  by  the  action  of  chlorine.  As  a  chemical  agent,  water  combines 
directly  with  other  substances,  it  aids  the  interaction  of  two  or  more 
substances,  and  is  responsible  for  such  common  processes  as  rusting 
and  decay. 

Oxygen  is  one  of  the  most  important  elements,  if  not  the  most 
important  element  known.  The  following  facts  may  be  taken  as  proof 
of  this  statement.  It  is  the  most  abundant  element,  and,  while  not  the 
most  active,  combines  with  nearly  all  the  other  elements.  Oxygen 
is  directly  responsible  for  the  changes  brought  about  by  the  breathing 
of  animals,  the  burning  of  fuels,  the  rusting  of  metals,  and  the  decay 
of  vegetable  and  animal  tissues.  Under  ordinary  conditions  oxygen 
is  a  gas.  It  has  an  allotropic  form,  known  as  ozone,  which  is  more 
active  than  oxygen.  Oxygen  may  be  prepared  in  a  number  of  ways 
by  the  decomposition  of  water  and  oxides,  and  from  the  atmosphere. 
So  wide  are  its  uses  that  about  4,000,000  cubic  feet  of  the  gas  are 
bottled  in  the  United  States  every  year. 

Hydrogen  is  the  lightest  known  substance.  While  ordinarily 
a  gas,  it  may  be  liquefied.  It  is  widely  distributed  in  nature  in  the 
form  of  compounds,  the  principal  one  of  which  is  water.  Hydrogen 
is  usually  prepared  from  water  or  acids  by  the  action  of  metals.  With 
the  exception  of  its  attraction  for  oxygen,  chlorine  and  a  few  other 
elements,  it  is  not  very  active.  The  greatest  usefulness  of  hydrogen 
is  in  its  combinations  with  these  few  elements,  such  as  oxygen,  carbon, 
chlorine,  and  nitrogen. 

An  atom  is  the  smallest  part  of  a  substance  that  can  react  with 
other  substances.  A  molecule  is  the  smallest  particle  of  a  substance 
that  can  exist  alone.     Molecules  are   composed  of  atoms.     Atoms 

5— 


66  CHEMISTRY  OF  THE  FARM  AND  HOME 

and  molecules  have  mass  or  weight.  Since  it  is  impossible  to  determine 
the  absolute  weight  of  these  very  small  particles  of  matter,  their  rel- 
ative weights  are  used.  In  the  case  of  atoms,  these  are  called  atomic 
weights;  in  the  case  of  molecules,  they  are  called  molecular  weights. 
Molecular  weights  are  the  sum  of  the  atomic  w^eights  of  the  substances 
composing  the  molecule.  Hydrogen  and  oxygen  are  taken  as  stand- 
ards for  atomic  weights. 

A  symbol  is  an  abbreviation  for  the  name  of  an  element.  A 
formula  is  used  to  represent  a  compound  and  is  a  group  of  symbols  of 
the  elements  composing  the  compound.  An  equation  is  an  expression, 
by  means  of  formulas,  of  a  chemical  reaction.  In  this  way  the  kinds 
of  matter,  their  proportions  by  weight,  and  if  gases,  their  proportions 
by  volume  may  be  conveniently  represented. 

QUESTIONS 

1.  What  conditions  affect  the  composition  of  natural  waters? 

2.  What  impurities  may  be  present  in  different  natural  waters? 

3.  Why   does   water   from   some   natural   springs   efTervesce? 

4.  What  are  important  characteristics  of  good  drinking  water? 

5.  Given  three  kinds  of  water,  distilled,  artesian  and  rain,  how 
could  you  determine  each  kind? 

6.  In  what  ways  can  water  be  decomposed? 

7.  Compare  the  solubility  of  solids  and  gases  in  water,  especially 
considering  the  effect  of  temperature  and  pressure  upon  the  amount 
of  material  dissolved. 

8.  What  are  some  of  the  principal  differences  between  oxygen 
and  hydrogen? 

9.  Compare  the  properties  of  ozone  with  those  of  oxygen. 

10.  State    some   tests   by  which  you  can  tell  the  differences  be- 
tween water  and  hydrogen  peroxide;  between  oxygen  and  ozone. 

11.  Would  pure  hydrogen  make  a  good  illuminating  gas?     Would 
a  Welsbach  burner  supplied  with  hydrogen  give  hght? 

12.  Is  it  safe  to  hunt  for  a  gas  leak  with  a  lighted  match? 

13.  What    is    meant    by  the  expressions:  combustion,  oxidation, 
slow  oxidation,  spontaneous  combustion? 

14.  What  phenomena  usually  accompany  combustion? 

15.  In  what    respect    does    the  rusting  of  iron  differ  from  the 
burning  of  iron  in  oxygen? 

16.  Does    anything    collect    on  the   inside   of  a  lamp   chimney 
when  first  lighted?     Does  it  remain  very  long? 

17.  Why    are    metal    cans  provided  for  the  oily  waste  in  wood 
turning   shops? 

18.  Describe  one  method  by  which    the    quantitative    relation 
of  hydrogen,  oxygen  and  water  may  be  proved. 

19.  State    what    is    meant  by  the  expressions:  atom,   molecule, 
formula,  equation,  catalytic  agent,  allotropic  form. 


CHAPTER  III 

THE  ATMOSPHERE  AND  ITS  CHIEF 
CONSTITUENT,  NITROGEN 

THE  ATMOSPHERE 

Introduction.  The  gaseous  mantle,  or  envelope,  sur- 
rounding our  earth  is  called  its  atmosphere.  It  is  also  com- 
monly called  the  air.  It  is  somewhat  like  a  gaseous  ocean 
with  a  depth  of  from  forty  to  fifty  miles,  though  it  is  be- 
lieved that  portions  of  its  gases  exist  as  far  as  two  hundred 
miles  from  the  earth's  surface.  The  atmosphere  is  a  mix- 
ture of  a  number  of  gases,  the  most  important  of  which 
are  nitrogen,  oxygen,  carbon  dioxide,  and  water  vapor. 
Some  of  its  ingredients  are  fairly  constant  in  amount,  while 
others  are  variable.  These  gases  possess,  in  the  aggre- 
gate, enormous  weight,  due  to  the  attractive  force  exerted 
between  the  earth  and  the  atmosphere.  This  amounts 
to  15  pounds  per  square  inch  at  sea  level,  or  41,300  tons 
for  each  acre  of  the  earth's  surface.  The  atmosphere 
furnishes  a  supply  of  oxygen  for  respiration.  Over  90% 
of  the  food  of  plants  comes  from  the  atmosphere  and  it  is 
a  valuable  factor  in  the  continual  round  of  certain  kinds  of 
matter,    as   water,   nitrogen,   etc. 

Composition  of  the  Air.  The  principal  components 
of  the  air  are  nitrogen  and  oxygen.  In  addition  to  these, 
water  vapor,  carbon  dioxide,  argon,  and  hydrogen  are  us- 
ually present.  Other  substances  are  sometimes  found,  de- 
pending upon  local  conditions.  These  are  ammonia,  oxides 
of  nitrogen,  sulphur  dioxide,  hydrogen  sulphide,  salts,  dust, 
and  bacteria.  I 

Nitrogen  is  the  most   abundant  compound  present   iH  \ 
the  air,  being  about  77.5%  by  volume  and  75.5%  by  weight. 


68  CHEMISTRY  OF  THE  FARM  AND  HOME 

Oxygen  is  next  in  quantity,  nearly  20.75%  by  volume 
and  23.2%  by  weight.  Argon  and  other  inert  gases  make 
another  one  per  cent  and  water  vapor  and  carbon  dioxide 
constitute  the  remaining  percentage.  The  constant  ingred- 
ients are  nitrogen,  oxygen,  argon,  helium,  hydrogen,  and  some 
rare  gases.  The  variable  ingredients  are  water  vapor,  carbon 
dioxide,   and  the  other  gases  and   substances  mentioned. 

Nitrogen.  Nitrogen  is  the  largest  and  least  variable 
component  of  the  air.  Although  so  abundant,  it  really 
plays  very  little  part  in  the  processes  going  on  in  the  atmos- 
phere. Indeed  its  chief  function  may  be  said  to  be  that 
of  a  diluent  for  the  oxygen  of  the  air.  In  other  words  it 
moderates  the  excessive  activities  of  the  latter  element 
and  helps  prevent  conflagrations  from  being  widespread. 
Nitrogen  has  always  been  in  the  atmosphere.  Little  by 
by  little  this  element  has  been  incorporated  into  the  soil 
by  different  agencies,  such  as  bacterial  life,  plants,  and 
electro-chemical  fixation.  Considerable  nitrogen  is  being 
removed  from  the  air  at  the  present  time.  Electrical 
thunderstorms  also  carry  nitrogen  to  the  earth  and  the 
electricity  generated  by  great  waterfalls  is  being  used  to 
accomplish  the  same  result.  It  is  seen,  therefore,  that 
nitrogen  is  being  taken  out  of  the  air  and  put  into  the  soil. 
On  the  other  hand,  there  are  certain  processes  which 
tend  to  return  nitrogen  to  its  vast  storehouse.  Such  are 
a  loss  of  this  element  from  soils  and  decaying  organic  matter 
by  denitrification,  and  a  return  of  nitrogen  in  the  processes 
of  combustion. 

Oxygen.  Oxygen  also  was  probably  present  in  the 
primeval  atmosphere  and  that  portion  which  was  left  after 
the  earth's  crust  was  fully  oxidized  and  formed  is  the  source 
of  the  present  atmospheric  oxygen.  It  is  the  most  active 
constituent  of  the  air.  The  air  is  calculated  to  contain 
ever  two  and  one  half  million  billions  of  pounds  of  oxygen. 
The  yearly  consumption  of  this  by  respiration  is  two  and 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     69 

one  quarter  billions  of  pounds.  It  would  require  over 
one  hundred  years  to  use  up  one  ten-thousandth  of  the 
total  supply  of  oxygen  in  this  way.  This  element  is  re- 
moved from  the  atmosphere  by  a  variety  of  processes.  The 
breathing  of  animals,  known  as  respiration,  the  burning  of 
fuels,  called  combustion,  the  true  respiration  of  plants, 
bacterial  processes,  oxidation  of  minerals,  and  other  similar 
steps  are  ways  in  which  oxygen  is  taken  out  of  the  air. 
Oxygen  is  returned  to  the  air  principally  by  the  process  of 
photosynthesis  of  plants.  On  account  of  the  large  number 
of  oxidation  processes  taking  place,  the  proportion  of  the 
element  is  subject  to  local  variations.  These  are  not  so 
great,  however,  as  might  be  expected,  on  account  of  the 
influence  of  diffusion,  wind,  and  the  compensating  action 
of  vegetation.  In  cities  and  over  marshy  places  the  amount 
of  oxygen  is  generally  found  to  be  slightly  less  than  in  the 
open  country  or  over  the  sea.  It  is  thought  that  the  air  is 
being  slowly  depleted  of  its  oxygen,  but  the  action  is  so 
slow  that  it  cannot  be  detected  at  the  present  time. 

Water  Vapor.  Water  vapor  is  an  exceedingly  variable 
constituent  of  the  air.  The  amount  depends  principally 
upon  the  temperature  and  proximity  to  bodies  of  water. 
With  either  increase  of  temperature  or  nearness  to  bodies 
of  water,  the  quantity  of  water  vapor  in  the  air  increases. 
At  0°C.  5.4  grams  of  vapor  are  contained  in  one  cubic  meter 
of  saturated  air.  At  10°  9.7  grams,  at  20°  17.1  grams  and 
at  30°  30  grams.  If  only  0.4  of  the  water  is  in  the  air  that 
the  latter  can  hold  at  any  given  temperature,  the  air  is  dry. 
If  0.8  of  the  maximum  capacity  of  water  is  in  the  air,  the 
latter  seems  moist,  or  humid.  In  such  cases  the  presence 
of  so  much  water  in  the  air  makes  conditions  very  oppres- 
sive for  animals  and  human  beings.  The  expressions  muggy 
and  dose  are  frequently  used  to  indicate  this  condition. 
If  the  temperature  is  low  and  the  atmosphere  near  the 
saturation  point,  the  cold  is  stinging  and  persons  feel  it 


70       CHEMISTRY  OF  THE  FARM  AND  HOME 

more  strongly  than  if  the  air  were  relatively  dry.  This 
explains  why  a  temperature  of  0°  or  10°F.  below  zero  near 
the  seacoast  or  the  great  lakes  affects  a  person  far  more 
than  20°  or  30°F.  below  zero  farther  north  or  inland  where 
there  is  very  little  moisture  in  the  air.  If  the  temperature 
is  high,  as  in  the  summer  time,  and  the  air  is  near  its  sat- 
uration capacity,  the  heat  is  felt  by  animals  far  more  than 
on  a  dry  warm  day,  because  the  evaporation  of  water  from 
the  animal  body  by  perspiration  is  prevented.  This  loss  of 
water  from  the  animal  body  lowers  the  temperature  of  the 
body  and  is  nature's  method  for  equalizing  the  temperature 
outside  and  in  the  body.  Air  is  saturated  with  water  vapor 
or  at  the  dew  point  when  the  slightest  reduction  of  tem- 
perature or  increase  of  pressure  causes  precipitation  of 
some  of  the  water. 

The  cycle  of  water  has  already  been  discussed.  We 
will  consider  in  this  connection  only  the  relation  of  the 
water  vapor  to  the  other  constituents  of  the  air.  When 
the  condensation  of  the  water  vapor  in  the  atmosphere  has 
reached  the  point  where  drops  of  water  are  formed,  these 
fall  to  the  ground  as  rain.  The  rain  carries  with  it  mechan- 
ically the  dirt  and  bacterial  impurities  of  the  air.  It  also 
carries  in  solution  some  of  all  the  gases  of  the  atmosphere. 
The  kind  and  amount  of  these  substances  will  of  course  vary 
depending  upon  the  particular  locaHty  of  the  rainfall.  That 
these  quantities  are  important  has  been  proved  in  many 
localities,  notably  at  the  Rothamsted  experiment  station 
in  England.  The  following  amounts  of  materials  were  found 
to  be  precipitated  along  with  rain  as  an  average  per  acre 
per  year  for  a  period  of  years.  Nitric  oxide  from  1.0  to  2.5 
lbs.,  sulphur  trioxide  17.25  lbs.,  ammonia  1.0  to  5.0  lbs., 
chlorine  in  combination  14.0  to  116.0  lbs.,  and  common 
salt  24.0  to  37.0  lbs.  It  can  be  quite  readily  understood 
that  the  constant  fall  of  these  substances,  small  as  they  may 
be  for  any  one  year,  will  in  time  be  considerable. 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     71 

Some  of  their  effects  are  quite  common  and  might 
be  mentioned  in  this  connection.  It  is  well  known  that 
grass  and  crops  in  general  show  a  more  luxuriant  growth  and 
have  a  healthier  color  after  a  thunderstorm  than  after  an 
ordinary  rainfall.  The  reason  is  that  oxides  of  nitrogen 
have  been  formed  by  the  electrical  disturbances  during  the 
thunderstorm  and  lightning  and  these  compounds  have 
been  brought  to  earth  by  the  rain.  Nitrogen  in  this  form 
is  a  very  active  fertilizer  and  stimulates  the  growth  of  the 
vegetation.  In  the  region  of  smelters  where  considerable 
sulphur  dioxide  is  given  off  into  the  atmosphere,  this  sub- 
stance is  carried  by  the  prevailing  winds  in  certain  directions 
and  in  time  is  brought  to  the  earth's  surface  by  rainfall. 
Wherever  the  dissolved  gases  come  in  contact  with  vegeta- 
tion they  act  as  poisons  and  all  plant  life  is  killed.  As  the 
natural  vegetation  dies,  there  is  nothing  to  hold  the  soil 
particles  together  and  erosion  results.  Moreover,  the 
ground  has  a  characteristic  light  color  indicating  that  the 
gases  in  the  rain  water  are  dissolving  out  the  easily  soluble 
minerals  and  leaving  practically  only  quartz  or  those  rock 
particles  that  are  rather  difficult  to  dissolve.  Another 
well  known  effect  of  atmospheric  gases  upon  plant  life  is 
seen  in  the  household.  It  is  sometimes  impossible  to  grow 
house  plants  successfully  since  the  products  from  the  com- 
bustion of  illuminating  or  fuel  gas  are  fatal  to  them. 

From  a  consideration  of  all  these  points  it  can  be  readily 
seen  that  rainfall  or  water  vapor  acts  as  a  purifier  of  the 
atmosphere.  The  moisture  of  the  air  is  very  serviceable 
as  one  stage  in  the  cycle  of  water  where  rainfall  is  the  im- 
portant succeeding  stage.  As  already  stated,  water  vapor 
also  serves  to  regulate  climatic  conditions  and  to  retain  the 
heat  rays  of  the  sun  upon  the  earth's  surface. 

Carbon  Dioxide.  This  substance  is  present  in  the  air  to 
a  comparatively  small  extent  when  the  other  constituents 
just  mentioned  are  considered.     It  is,  however,  one  of  the 


72  CHEMISTRY  OF  THE  FARM  AND  HOME 

most  important  substances  present  there  and  serves  a  num- 
ber of  vital  functions.  Life  as  it  now  exists  on  the  earth  is 
absolutely  dependent  upon  the  carbon  dioxide  of  the  air. 
If  it  were  removed  the  earth  would  very  soon  become  a  bar- 
ren waste.  In  the  atmosphere  of  the  open  country  or  over 
the  sea,  carbon  dioxide  amounts  to  about  0.03%  by  volume, 
in  other  words  about  three  parts  per  ten  thousand.  Over 
cities,  where  considerable  fuel  is  consumed,  the  percentage 
of  carbon  dioxide  increases  to  0.06%,  and  in  crowded  rooms 
the  quantity  may  be  six  or  eight  times  as  high  as  the  last 
figure.  If  the  proportion  of  carbon  dioxide  is  over  0.06%, 
the  air  is  said  to  be  foul,  not  so  much  on  account  of  the  car- 
bon dioxide  itself  as  on  account  of  the  decaying  organic 
matter  which  is  exhaled  along  with  it  from  the  lungs  of  human 
beings.  The  quantity  of  carbon  dioxide  in  the  atmosphere 
of  a  room  thus  serves  as  an  index  to  the  amount  of  poison- 
ous material  present. 

It  is  estimated  that  the  total  amount  of  carbon  dioxide 
present  in  the  atmosphere  over  an  acre  of  land  is  about 
thirty  tons.  Evidently,  then,  the  relatively  small  amount 
of  0.03%  by  volume  means  considerable  when  applied  to 
a  rather  large  amount  of  air.  The  total  amount  of  this  gas 
in  the  atmosphere  of  the  globe  is  estimated  to  weigh  over 
5,000  biUions  of  tons. 

Carbon  dioxide  enters  the  atmosphere  in  numerous 
ways.  The  respiration  of  animals,  the  burning  of  fuels, 
the  escape  of  underground  gases,  volcanic  gases,  the  de- 
composition of  organic  matter,  all  serve  to  continually  re- 
inforce the  supply  of  this  ingredient.  On  the  other  hand, 
nature  has  provided  certain  means  by  which  the  gas  is 
removed  from  the  air,  and  the  quantity  never  increases, 
except  under  local  conditions  and  for  a  temporary  period. 
It  should,  however,  be  stated  that  the  proportion  of  carbon 
dioxide  is  greater  during  the  night  than  during  the  day- 
time over  the  land.    It  has  been  shown  that  during  the 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     73 

day  there  are  2.78  parts  per  ten  thousand  while  at  night 
there  are  2.82  parts.  Over  the  sea  this  daily  variation  can- 
not be  detected. 

The  rainfall  removes  considerable  carbon  dioxide  in 
solution.  Growing  plants  secure  all  their  carbon  from 
atmospheric  carbon  dioxide.  This  is  the  chief  process  which 
tends  to  diminish  its  quantity.  The  extent  of  this  removal 
of  carbon  dioxide  from  the  air  by  plants  is  simply  enormous. 
About  half  of  the  dry  matter  of  plants  consists  of  carbon 
all  of  which  comes  from  the  atmosphere.  An  average  acre 
crop  of  mangels  abstracts  from  the  air,  before  reaching  ma- 
turity, about  3,500  pounds  of  carbon,  which  represents  the 
carbon  dioxide  in  a  200-foot  layer  of  air  over  some  180  acres. 

The  amount  of  carbon  dioxide  in  the  atmosphere  is  con- 
tinually being  affected  by  the  addition  and  removal  of  the 
gas  in  the  different  ways  indicated.  The  two  processes 
approximately  balance  each  other,  and,  as  far  as  can  be 
learned  by  analysis,  the  proportion  of  the  gas  in  the  at- 
mosphere is  apparently  uniform  within  the  limits  stated. 

Ammonia.  Ammonia  is  one  of  the  ordinary  products 
of  the  decay  and  decomposition  of  organic  matter.  Waste 
animal  matter  evolves  ammonia  gas  more  or  less  quickly. 
The  pungent  odor  in  the  vicinity  of  manure  piles  and  stables 
is  characteristic  of  ammonia.  This  gas  diffuses  through 
the  atmosphere  and  is  returned  to  the  earth  in  the  rainfall. 
Since  nitrogen  in  the  form  of  ammonium  salts  is  a  plant  food, 
it  can  readily  be  seen  that  this  process  is  an  important 
one  to  return  nitrogen  to  active  circulation  and  help  plant 
growth.  That  the  amount  of  nitrogen  recovered  for  life 
processes  is  considerable  has  already  been  stated  under  the 
effect  of  rainfall  upon  atmospheric  gases. 

Less  Important  Constituents  of  the  Air.  Hydrogen 
exists  in  small  quantities  in  the  atmosphere.  Some  experi- 
ments made  with  the  air  of  Paris  show  that  100  liters  of  it 
contain  about  19  cubic  centimeters  of  hydrogen. 


74       CHEMISTRY  OF  THE  FARM  AND  HOME 

Argon  is  a  constituent  which  is  next  to  nitrogen  and 
oxygen  both  in  constancy  and  total  amount  present.  It  is 
heavier  than  oxygen  and  is  more  soluble  in  water  than 
nitrogen.     But  argon  is  almost  without  chemical  activity. 

Helium  was  known  to  be  present  in  the  atmosphere  of 
the  sun  long  before  it  was  found  on  the  earth.  It  occurs 
not  only  in  the  atmosphere  but  in  a  few  minerals,  springs, 
and  a  meteorite.  It  is  probably  less  soluble  in  water  than 
any  other  gas. 

Ozone  is  present  in  the  air  in  variable  amounts,  always 
very  small.  In  towns  and  over  marshes  it  is  rarely  found, 
because,  if  present,  it  would  react  very  quickly  with  other 
substances  and  lose  its  own  identity.  It  is  most  abundant 
during  May  and  June,  especially  after  severe  thunderstorms 
or  gales.  It  is  doubtful  whether  its  presence  in  the  atmos- 
phere has  any  beneficial  effect  upon  persons  breathing  it, 
but  it  would  seem  that  its  presence  proves  that  the  air  is 
free  from  oxidizable  organic  matter  and  micro-organisms. 

Atmospheric  Dust.  It  is  a  well  known  fact  that  there" 
is  usually  dust  in  the  atmosphere.  This  fine  material  of 
mineral,  organic,  or  bacterial  origin  settles  in  a  thin  deposit 
over  furniture  and  all  parts  of  a  building.  Even  though  a 
house  may  not  be  in  use,  the  dust  is  still  present,  finding 
its  way  into  the  building  under  the  influence  of  drafts  or 
wind  currents.  Dust  storms  and  even  sand  storms  are  of 
frequent  occurrence  in  certain  parts  of  the  globe.  Generally 
the  circulation  of  dust  may  not  be  of  any  great  moment 
beyond  the  inconvenience  of  keeping  a  house  with  its  contents 
clean;  but  in  some  instances  it  may  result  in  changes  of 
great  economic  importance.  Disease  is  undoubtedly  spread 
in  this  manner.  In  many  cases  the  whole  depth  of  tillable 
soil  has  been  swept  away  by  a  violent  wind  storm.  Some- 
times sand  carried  by  wind  has  even  drilled  its  way  through 
the  glass  panes  of  lighthouses  and  houses  along  the  seashore. 
Probably  every  student  is  familiar  with  the  effect  of  the 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     75 

wind  in  laying  down  dirt  and  soil  against  fences  and  uneven 
places  in  a  field  or  road.  There  are  vast  areas  of  soils  in 
the  Mississippi  valley  and  in  parts  of  China  which  were 
formed  by  the  wind.  The  general  name  aeolian  is  applied 
to  such  soils.  Loessial  and  adobe  soils  are  included  under 
this  head. 

Micro-Organisms.  These  are  most  abundant  in  towns 
or  wherever  organic  substances  are  undergoing  decay.  They 
are  important,  since  they  may  spread  disease,  distribute 
yeasts  and  moulds  which  cause  fermentation  and  decay, 
and  scatter  the  particular  organisms  which  are  responsible 
for  the  fixation  of  atmospheric  nitrogen. 

Salts.  In  some  instances  large  quantities  of  salts  have 
been  proved  to  be  in  the  atmosphere.  They  are  chiefly 
common  salt  which  has  been  carried  inland  by  the  ocean 
breezes.  The  ocean  fogs  and  the  fine  mists  caused  by  the 
breaking  of  waves  upon  rocky  coasts,  contain  much  salt. 
In  this  finely  divided  form,  such  substances  can  be  carried 
considerable  distances  by  winds.  The  common  dust  of 
wind  storms  and  especially  the  alkali  dust  from  the  arid 
plains  contain  salts.  Though  they  may  not  be  of  any  great 
moment  they  are  worth  mentioning,  as  they  undoubtedly 
influence  soil  fertility. 

The  Air  Is  a  Mixture.  The  proportions  of  the  chief  con- 
stant constituents  of  the  air  have  been  determined  in  many 
different  localities.  They  have  been  found  to  be  practically  the 
same  everywhere.  This  condition  is  certainly  remarkable, 
but  is  undoubtedly  the  result  of  the  circulation  of  air  and 
the  rapid  diffusion  of  its  gases.  On  account  of  the  quite 
constant  proportion  of  oxygen  and  nitrogen  of  the  air,  it 
might  be  supposed  that  the  air  is  a  compound.  A  number 
of  considerations,  however,  prove  that  this  is  not  so:  (1) 
When  proper  quantities  of  oxygen  and  nitrogen  are  mixed, 
there  is  no  evidence  of  union  such  as  change  of  color,  volume, 
or  physical  condition,  evolution  of  heat,  etc.     (2)  Liquid 


76       CHEMISTRY  OF  THE  FARM  AND  HOME 

air  has  a  different  proportion  of  oxygen  and  nitrogen  than 
normal  air  has.  Moreover,  Uquid  nitrogen  can  easily  be 
separated  from  liquid  oxygen,  since  it  boils  away  first. 
(3)  Normal  air  has  about  21  volumes  of  oxygen  and  78 
volumes  of  nitrogen.  But  air  which  has  been  dissolved  in 
water  has  35  volumes  of  oxygen  and  65  volumes  of  nitrogen. 
If  the  air  were  a  compound,  the  proportion  of  gases  ought 
to  be  the  same  in  both  cases. 

NITROGEN 

Introduction.  Nitrogen  is  the  chief  constituent  of  the 
atmosphere  by  volume  and  by  weight.  It  is  one  of  the 
most  essential  elements  of  plant  and  animal  life.  Yet  as 
a  simple  and  elementary  substance  it  is  characterized  by 
extreme  inactivity.  Its  compounds  are,  on  the  other  hand, 
sometimes  extremely  active,  in  fact  dangerously  so.  Its 
relative  inertness  is  indicated  by  the  name  azote  which 
is  sometimes  used  and  means  non-life  supporting. 

Distribution.  Nitrogen  occurs  in  nature  in  both  the  free 
and  the  combined  state.  In  the  free  form  it  constitutes 
practically  four  fifths  by  volume  and  three  quarters  by 
weight  of  the  atmosphere.  The  actual  proportion  is  77.5 
parts  per  100  by  volume.  In  the  combined  condition 
nitrogen  exists  in  many  compounds  found  in  mineral,  animal 
and  vegetable  matters.  The  largest  mineral  deposit  of  nitrogen 
is  found  in  Chile  and  Peru  in  the  compound  sodium  nitrate, 
commonly  called  Chile  saltpetre.  Other  deposits  of  the 
same  material  are  reported  for  the  peninsula  of  lower  Cali- 
fornia and  some  other  localities  situated  in  a  dry  climate. 
Small  deposits  of  ordinary  saltpetre,  niter,  or  potassium 
nitrate,  are  found  in  the  earth  in  India.  It  is  reported  that 
accumulations  of  nitrates  are  gradually  being  formed  in 
certain  parts  of  Colorado.  Fertile  soils  contain  very  small 
quantities  of  nitrates  of  potassium,  sodium,  and  calcium. 
Nitrogen  is  also  present  in  other  forms  in  the  soil. 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     77 

Soft  coal  contains  a  small  percentage  of  nitrogen,  rang- 
ing from  0.5  to  2%.  When  this  coal  is  heated  in  the  process 
of  preparing  illuminating  gas,  the  nitrogen  is  given  off  as 
ammonia  and  may  be  recovered  as  a  by-product  in  the 
compound,  ammonium  sulphate. 

In  the  vegetable  kingdom  nitrogen  exists  in  a  number 
of  complex  compounds.  The  most  valuable  constituents  of 
foods,  such  as  the  gluten  of  wheat  flour,  and  many  medi- 
cinal substances,  like  quinine  and  morphine,  contain  nitro- 
gen. 

A  great  proportion  of  the  matter  of  animal  origin  is 
nitrogenous.  Egg  albumin,  the  casein  of  milk,  and  the 
fibrin  of  meat  are  examples  of  food  products  which  are 
valuable  for  their  content  of  nitrogen.  The  human  body 
contains  2.4%  nitrogen. 

Cycle  of  Nitrogen.  The  terrestrial  supply  of  nitrogen 
may  be  looked  upon  as  being  in  two  portions.  That  in  the 
atmosphere  is  called  the  inactive  stock  and  that  in  plant  and 
animal  life  and  in  mineral  deposits  is  called  the  active  stock. 
The  quantity  of  nitrogen  in  the  air  is  very  great.  This  is 
not  very  active  and  does  not  readily  combine  with  other 
elements  to  form  compounds  of  nitrogen.  During  thunder- 
storms oxides  of  nitrogen  may  be  formed  from  this  source 
and  these  may  be  brought  to  the  earth's  surface  by  the  rain- 
fall. There  are  numerous  kinds  of  bacteria  which  are  capa- 
ble of  taking  nitrogen  from  the-  air  also.  One  of  the  most 
familiar  examples  of  these  is  the  class  of  bacteria  that  is 
actively  associated  with  leguminous  plants,  as  peas,  beans, 
clover,  alfalfa,  etc.  The  nodules  formed  by  these  bacteria 
on  the  roots  of  such  plants  often  contain  over  5%  of  com- 
bined nitrogen  which  is  afterward  digested  and  absorbed  by 
the  roots  of  the  plant.  Some  of  this  nitrogen  is  left  in  the 
soil  after  the  plant  dies.  In  fact  all  the  nitrogen  present  in 
the  soil  originally  came  from  the  atmosphere.  Nitrogen  is 
taken  out  of  the  soil  by  plants  and  the  latter  are  consumed 


78  CHEMISTRY  OF  THE  FARM  AND  HOME 

by  animals.  When  plants  and  animals  die,  they  undergo 
decomposition  by  bacterial  action  and  the  nitrogen  is  again 
set  free  either  as  nitrogen  or  ajB  simple  compounds,  such  as 
ammonia  and  oxides  of  nitrogen.  There  is  a  gradual  slow 
return  of  some  of  this  nitrogen  to  the  air  by  the  rotting  of 
organic  matter,  especially  denitrification,  and  by  the  burn- 
ing of  fuels  and  other  substances  of  vegetable  or  animal 
origin.  The  cycle  of  nitrogen  is  illustrated  diagrammatically 
in  Figure  20. 

Preparation.     Nitrogen  may  be  prepared  from  the  atmos- 
phere or  a  few  of 

ANIMAU    UIFE.   y/^  ^N^^.^ACTERlAl- L.IFE.         itS         COmpOUndS. 

It  may  be  pre- 
pared from  the 
air  by  first  ab- 
sorbing the  other 
PL.ANT  i-irEi  \^  ^/-THE.  soiu  substauces  pres- 

ent, leaving  the 

Figure  20. — The  cycle  of  nitrogen.  . .  rr\i 

nitrogen.  There 
are  some  elements,  however,  which  are  not  removed 
by  this  method  and  they  are  mixed  with  the  nitro- 
gen resulting  from  the  treatment.  In  order  to  carry 
on  the  process  it  is  better  to  choose  a  substance  which 
will  combine  with  the  oxygen  and  form  a  product  not  a  gas. 
This  facilitates  the  separation  from  the  nitrogen.  Phos- 
phorus and  copper  are  the  substances  most  commonly  used 
for  this  purpose. 

(1)  By  the  action  of  phosphorus.  A  small  piece  of  phos- 
phorus is  placed  in  a  dish  upon  a  cork  and  floated  in  water. 
It  is  ignited  by  a  hot  wire  and  a  large  bottle  is  placed  over 
it  so  as  to  confine  the  volume  of  air  concerned  in  the  experi- 
ment. The  phosphorus  combines  with  the  oxygen  of  the 
air  to  form  phosphorus  pentoxide  which  is  soluble  in  the 
water.  The  nitrogen  is  left  unchanged.  The  water  rises  to 
take  the  place  of  the  oxygen  withdrawn  by  the  reaction. 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     79 

(2)  By  the  action  of  copper.  Figure  19,  which  shows 
the  method  of  proving  the  relations  by  weight  of  the  con- 
stituents of  water,  illustrates  a  simple  device  which  can  be 
used  for  the  preparation  of  nitrogen.  A  current  of  air  is 
slowly  passed  in  at  the  left  of  the  tube  which  contains  a 
quantity  of  copper.  The  latter  is  heated  and  combines 
readily  with  the  oxygen  of  the  air.  The  nitrogen  passes  on 
and  may  be  collected  by  displacement  of  water  in  bottles, 
as  in  the  preparation  of  hydrogen  and  oxygen. 

Nitrogen  may  also  be  prepared  by  decomposing  certain 
of  its  compounds  in  such  a  way  as  to  liberate  the  gas  itself. 
If  ammonium  nitrite  is  heated,  nitrogen  and  water  vapor 
are  the  products.  The  gas  can  be  collected  in  the  usual 
manner  over  water.  This  method  gives  practically  pure 
nitrogen.  In  fact  the  differences  in  the  properties  of  the  ni- 
trogen prepared  in  this  way  and  that  from  the  atmosphere 
led  to  the  discovery  of  the  inert  gases  of  the  atmosphere. 

Physical  Properties.  At  ordinary  temperatures  nitrogen 
is  a  colorless,  odorless,  and  tasteless  gas.  It  is  slightly 
lighter  than  the  air,  one  liter  weighing  1.25  grams.  Nitro- 
gen is  only  very  slightly  soluble  in  water  (1.6  volumes  in 
100),  much  less  than  oxygen.  It  may  be  liquefied  by  lower- 
ing to  —  146°C.  under  35  atmospheres  of  pressure  and 
solidified  by  cooling  to  —  214°C. 

Chemical  Properties.  Under  ordinary  conditions  nitro- 
gen is  extremely  inactive.  This  is  its  most  characteristic 
property.  It  neither  burns  nor  does  it  support  combus- 
tion. Neither  does  it  directly  enter  into  combination 
with  other  elements  at  ordinary  temperatures.  It  may, 
though,  combine  with  a  few  substances  such  as  aluminium 
and  magnesium,  if  brought  into  contact  with  them  at  a  red 
heat.  These  compounds  are  called  nitrides,  just  as  some 
oxygen  compounds  are  called  oxides.  Under  the  influence 
of  electrical  discharges  nitrogen  combines  with  hydrogen; 
also  under  the  same  conditions  it  combines  with  oxygen.  On 


80       CHEMISTRY  OF   THE  FARM  AND  HOME 

account  of  this  property  we  are  able  at  the  present  time  to 
take  nitrogen  out  of  the  air  by  artificial  means. 

Nitrogen  is  not  poisonous  to  animals,  for  they  con- 
stantly inhale  it  from  the  atmosphere;  but  life  would  be 
impossible  in  pure  nitrogen,  because  it  would  exclude  oxy- 
gen which  is  necessary  for  respiration.  Nitrogen  enters 
into  the  composition  of  a  large  number  of  compounds.  In 
direct  contrast  to  the  relative  inactivity  of  the  element 
itself,  some  of  these  compounds  are  active  to  a  high  degree. 
Nitroglycerine,  for  example,  is  highly  explosive.  Many 
nitrogenous  animal  and  vegetable  compounds  decompose 
easily.  Nitric  acid  and  ammonia  are  both  active  and  are 
much  used  in  the  laboratory  and  manufacturing  processes. 

Compounds  of  Nitrogen.  Of  the  compounds  of  nitrogen, 
only  a  few  will  be  considered.  The  two  most  important  are 
ammonia  and  nitric  acid. 

Before  these  two  compounds  of  nitrogen  are  studied, 
however,  let  us  consider  a  few  general  terms  that  will  be 
used  very  frequently  from  now  on  in  the  study  of  chemistry. 

ACIDS,  BASES,  SALTS 

Acids.  Mention  has  been  made  several  times  of  acids, 
especially  under  the  topic  of  hydrogen.  Can  you  recall  the 
relation  which  was  stated  to  exist  between  acids  and  the  ele- 
ment hydrogen?  As  commonly  understood  there  are  at  least 
four  characteristics  of  substances  designated  by  the  general 
name  of  acid,  though  every  acid  does  not  necessarily  possess  all 
these  properties.  They  are  (1)  a  sour  taste,  (2)  their  water 
solutions  turn  blue  litmus  red,  (3)  they  react  with  metals 
with  the  liberation  of  hydrogen,  and  (4)  they  combine  with 
bases  to  form  salts. 

Besides  the  chemical  acids  of  the  laboratory  and  com- 
merce, such  as  hydrochloric,  nitric,  and  sulphuric  acids, 
there  are  a  number  of  common  substances  which  contain 
acids.     A  few  examples  are  fruit  juices,  vinegar,  sour  milk, 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     81 

and  rancid  butter.  Acids  may  contain  one  or  more  hydro- 
gen atoms  which  can  be  replaced  by  a  metal ;  those  with  one 
hydrogen  atom  are  called  monobasic,  those  with  two  hydro- 
gen atoms  are  known  as  dibasic  and  so  on. 

Bases.  The  name  base  is  applied  to  those  substances 
which  unite  with  acids  and  form  salts.  They  are  either 
hydroxides  or  oxides  of  the  metals.  The  strong  bases, 
which  are  very  soluble  in  water,  such  as  the  hydroxides  of 
sodium,  potassium,  and  calcium,  are  called  alkalies.  The 
name  caustic  is  often  applied  to  them  on  account  of  their 
corrosive  action.  The  alkalies,  or  those  bases  which  are 
soluble  in  water,  turn  red  litmus  blue  and  have  a  bitter  or 
acrid  taste.  Substances  which  affect  litmus  in  this  way  are 
said  to  have  an  alkaline  reaction.  Alkalies  contain  the 
hydroxyl  group,  or  radicle,  OH.  If  one  radicle  is  present, 
they  are  called  monacid;  if  two  radicles,  diacid,  etc. 

Salts.  A  salt  is  the  main  product  of  the  interaction  of 
an  acid  and  an  alkali  or  base.  Water  is  another  product  of 
such  a  reaction.  This  process  is  commonly  known  as 
neutralization,  and  salts  are  generally  neutral  in  reaction  to 
litmus.  A  salt  is  composed  of  the  metal  of  the  base  and  the 
elements  of  the  acid  other  than  the  hydrogen.  Salts  may 
also  be  formed  in  other  ways,  as,  for  example,  the  action  of 
an  acid  upon  a  metal,  or  by  the  action  of  an  acid  upon  a 
carbonate. 

Some  examples  of  reactions  involved  in  the  formation  of 
salts  are  shown  by  the  following  equations. 

HCl  +  NaOH  -^  NaCl  +  H2O 

H2SO4  +  2  KOH  -^  K2SO4  +  2  H2O 

2  HNO3  +  Ca(0H)2  -^  Ca(N03)2  +  2  H2O 

Zn  +  H2SO4   -^  ZnS04  +  H2 

2  HCl   +    CaC03    -^  CaCl2  +  CO2  +  H2O 

Salts  in  which  all  the  hydrogen  atoms  are  replaced  by 
metals  are  called  normal  salts.     If  some  of  the  hydrogen  is 


82       CHEMISTRY  OF  THE  FARM  AND  HOME 

not  replaced,  they  are  called  acid  salts.  When  some  of  the 
hydroxyl,  or  OH  radicles,  of  a  base  is  not  replaced,  a  basic 
salt  results.  Are  there  any  examples  of  each  of  these  dif- 
ferent kinds  of  salts  in  the  above  equations?  In  addition 
to  the  formation  of  a  salt  in  neutralization,  what  com- 
pound seems  to  be  characteristic  of  that  reaction? 

AMMONIA,  NH3 

Distribution.  Ammonia  is  found  in  nature  in  both  the 
free  and  combined  forms.  Free  ammonia  occurs  only  in 
small  quantities  in  the  atmosphere,  part  of  this  supply 
being  given  off  from  decaying  organic  matter  and  part 
being  produced  by  discharges  of  electricity  during  rain- 
storms. Some  combined  ammonia  is  found  in  the  air  and 
in  plant  and  animal  products. 

Preparation.  Ammonia  may  be  prepared  by  heating 
ammonium  compounds  with  or  without  a  strong  base,  as 
slaked  lime.  The  simplest  method  for  laboratory  purposes 
is  to  heat  a  small  portion  of  the  concentrated  ammonium 
hydroxide,  commonly  called  ammonia  water.  Another 
method  is  to  heat  a  mixture  of  equal  parts  of  slaked  lime 
and  an  ammonium  compound,  as  ammonium  chloride. 

2NH4CI  +  Ca(0H)2  -^  2NH3  +  2H2O  +  CaCl2 

The  ammonia  of  commerce,  however,  is  a  by-product  of 
the  dry  distillation  of  organic  matter,  such  as  bones,  soft 
coal,  etc.  In  this  way  the  nitrogen  is  recovered  in  the  form  of 
ammonia  from  waste  animal  matter  and  from  the  manufac- 
ture of  illuminating  gas.  Since  the  gas  is  very  soluble  in 
water,  it  is  either  collected  over  mercury  or  by  upward 
displacement  of  air.     It  can  be  dried  over  quicklime. 

Physical  Properties.  Ammonia  is  a  colorless  gas  with  a 
strong  pungent  odor  and  taste.  It  is  0.59  times  as  heavy  as 
the  air,  one  liter  under  standard  conditions  weighing  0.762 
gram.  It  is  very  soluble  in  water,  one  cubic  centimeter 
of  water  at  standard  conditions  absorbing  1,146  cubic  cen- 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     83 


timeters  of  the  gas.  Water  solutions  of  the  gas  have  a 
lower  specific  gravity  than  water  itself,  the  more  gas  dis- 
solved, the  lower  the  density.  All  the  ammonia  can  be 
expelled  by  heating.  Under  favorable  conditions  charcoal 
absorbs  90  times  its  volume  of  ammonia  gas.  The  great 
solubility  of  ammonia  in  water  is  plainly  shown  by  the  so- 
called  aw  wowm /oww/a^'w.  Figure  21.  The  flask  A  is  filled 
with  dry  ammonia  gas.  The  tube 
B  with  a  stopper  is  fitted  into  the 
flask  and  the  lower  end  placed  in  a 
volume  of  water  containing  a  few 
drops  of  litmus  solution.  The  action 
can  be  started  by  blowing  a  little 
water  up  from  the  lower  end  of  the 
tube  B.  The  ammonia  dissolves  in 
the  water  so  rapidly  that  a  vacuum 
is  formed  in  the  flask  and  more 
water  is  forced  up  by  atmospheric 
pressure.  The  action  is  main- 
tained until  all  the  ammonia  is  dis- 
solved. If  the  upper  end  of  the  tube 
is  drawn  to  a  rather  fine  opening, 
the  water  rushes  up  with  such  force 
n  that  it  is  sprayed  in  all  directions 

^^Hj- — ^  ^s  it  hits  the  bottom  of  the  flask. 

Figure  21— The  ammonia     The  ammouia  solution  tums  the  lit- 

fountain.  ^^^    ^^j^^^ 

Ammonia  is  an  example  of  a  gas  that  can  be  liquefied 
by  pressure  at  a  temperature  only  slightly  below  zero. 
Liquid  ammonia  is  0.6  times  as  heavy  as  water,  boils  at 
—  40°C.  and  freezes  at  —  75°C.  Its  greatest  usefulness  is  as  a 
refrigerating  agent  and  for  the  manufacture  of  artificial  ice. 
The  ammonia  is  continually  passed  through  a  change  from 
the  liquid  to  the  gaseous  state  and  from  the  gaseous  to  the 
liquid  form.     The  gas  is  liquefied  by  compression  and  the 


84       CHEMISTRY  OF  THE  FARM  AND  HOME 

heat  thus  liberated  removed  by  flowing  water  which  sur- 
rounds the  pipes.  The  Uquid  then  passes  into  other  pipes 
immersed  in  calcium  chloride  brine  and  is  allowed  to  evap- 
orate, the  gas  returning  to  the  compressor.  The  heat 
necessary  for  this  vaporization  is  taken  from  the  brine  which 
is  partially  frozen.  The  freezing  mixture  of  ice  and  brine 
thus  formed  is  then  distributed  to  the  localities  to  be  cooled. 

The  ammonia  and  brine  remain  in  their  respective 
systems  of  pipes  and  are  used  over  and  over  again.  There 
is  some  loss  of  ammonia,  however,  by  the  process.  Liquid 
sulphur  dioxide  and  liquid  carbon  dioxide  may  also  be  used 
to  manufacture  artificial  ice  in  a  similar  manner. 

Chemical  Properties.  Ammonia  does  not  burn  in  the 
air,  but  it  does  burn  in  pure  oxygen,  forming  water  and 
nitrogen.  It  does  not  support  combustion.  Ammonia  is 
a  fairly  active  substance,  though,  and  combines  readily 
with  chlorine,  hydrochloric  acid,  and  other  acids.  Its  watar 
solution  turns  red  litmus  paper  blue  and  is,  therefore,  an 
alkali.  With  acids  ammonia  unites  directly  and  forms  a 
series  of  ammonium  compounds.  If  a  bottle  of  ammonium 
hydroxide  and  one  of  hydrochloric  acid  are  unstoppered 
and  placed  side  by  side  dense  fumes  of  ammonium  chloride 
are  formed. 

NH4OH  +  HCl  -^  NH4CI  +  H2O 

Composition  of  Ammonia.  It  is  possible  to  take  advan- 
tage of  the  reaction  of  chlorine  with  ammonia  to  prove  the 
volumetric  composition  of  ammonia.  The  tube  shown  in 
Figure  22  is  filled  with  saturated  salt  solution  which  is  then 
displaced  with  chlorine  gas.  After  the  stopcock  is  closed, 
concentrated  ammonia  water  is  run  into  the  chlorine  drop 
by  drop.  The  hydrogen  and  the  chlorine  react  quickly 
forming  hydrochloric  acid,  and  the  nitrogen  is  left  as  a  gas. 
The  experiment  is  completed  by  allowing  dilute  sulphuric 
acid  to  be  drawn  into  the  tube  to  take  the  place  of  the  hy- 
drogen and  chlorine  which  have  combined.     The  volume  of 


K 


TP 


U 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     85 

the  nitrogen  remaining  is  one  third  that  of  the  original 
chlorine.  As  hydrogen  and  chlorine  combine  in  equal  parts 
(see  later)  the  volume  of  nitrogen  is  to  the  volume  of  chlo- 
rine as  one  is  to  three,  and  the  volume  of  nitrogen  is  to  the 
volume  of  hydrogen  as  one  is  to  three. 

NITRIC  ACID,  HNO3 

Preparation.  Nitric  acid  may  be  prepared  by  heating 
sodium  nitrate  or  any  other  nitrate  with  sul- 
phuric acid  in  a  retort.  The  nitric  acid  is 
volatile  and  may  be  condensed  as  it  dis- 
tills   over. 

NaNOa  +  H2SO4  ->  HNO3  +  HNaS04. 
See  Figure  23.  Another  commercial  process 
is  the  direct  union  of  atmospheric  nitrogen 
and  oxygen  by  means  of  an  electrical  dis- 
charge. The  nitrogen  peroxide,  NO2,  thus 
formed  is  dissolved  in  water  giving  nitric 
acid,  and  nitric  oxide,  NO,  which  unites 
with  the  oxygen  of  the  air  to  give  more 
nitrogen  peroxide. 

Physical     Properties.      The     anhydrous 
(without    water)  acid  is  a  thick  colorless  oil 
with  a  specific  gravity  of  1.56.     It  is  easily 
paratus  %o  prove  dccomposed  by  hcat  and  light,  and  solutions 

the  volumetric  ,  ,. 

composition  of  am-  Consequently  become  brown  upon  standmg. 

Chemical  Properties.  This  substance 
has  the  properties  of  an  acid  and  is  also  a  powerful  ox- 
idizing agent.  These  two  characteristics  should  be  kept 
clearly  in  mind.  Whereas  metals  usually  liberate  hydro- 
gen from  acids,  this  reaction  occurs  with  nitric  acid  in 
only  a  few  cases.  The  hydrogen  reduces  the  nitric  acid 
just  as  rapidly  as  it  is  set  free,  and  water,  nitric  oxide,  and 
even  ammonia  are  formed. 

When  one  volume  of  nitric  acid  is  mixed  with  three 


86 


CHEMISTRY  OF  THE  FARM  AND  HOME 


volumes  of  hydrochloric  acid,  they  form  what  is  known  as 
aqua  regia,  a  liquid  which  dissolves  gold,  the  king  of  metals. 
The  action  of  this  liquid  is  due  to  the  liberation  of  chlorine 
which  acts  strongly  upon  gold  and  platinum. 

Nitric  acid  also  vigorously  oxidizes  other  materials  than 
metals;  for  example,  sulphur  is  converted  into  sulphuric 


Figure  23. — The  preparation  of  nitric  acid. 

acid,  a  piece  of  glowing  carbon  may  be  completely  burned 
in  concentrated  nitric  acid,  and  organic  dyes  are  changed  to 
colorless  bodies.  This  acid  affects  protein  substances  in  a 
characteristic  manner,  namely,  it  turns  them  yellow,  a 
reaction  commonly  called  xaniho-pr oleic. 

Usefulness.  Nitric  acid  and  nitrates  have  a  number  of 
important  industrial  applications.  The  acid  is  used  for  the 
manufacture  of  nitrobenzene  for  perfume,  nitroglycerine 
and  nitro-cellulose  or  guncotton  for  explosives  and  col- 
lodion and  celluloid  prepared  from  nitro-cellulose.  The 
salts  of  nitric  acid  are  also  used  in  the  manufacture  of  ex- 
plosives and  for  the  preservation  of  meats. 
OXIDES  OF  NITROGEN 

Nitrogen  forms  a  series  of  five  oxides,  the  names  and  the 
formulas  of  which  are  as  follows;  nitrous  oxide,  N2O,  nitric 


ATMOSPHERE  AND  ITS  CONSTITUENT  NITROGEN     87 

oxide,  N2O2  (or  NO),  nitrogen  trioxide,  N2O3,  nitrogen 
tetroxide,  or  nitrogen  peroxide,  N2O4  (or  NO2),  nitrogen 
pentoxide,  N2O5.  Of  these  only  nitrous  oxide,  nitric  oxide 
and  nitrogen  peroxide  will  be  considered. 

Nitric  Oxide.  This  substance  is  prepared  by  the  action 
of  dilute  nitric  acid  upon  copper.  It  is  a  colorless  gas  with 
the  characteristic  property  of  combining  directly  with 
oxygen  to  form  nitrogen  peroxide,  NO  2.  It  supports  the 
combustion  of  phosphorus  but  not  of  sulphur  and  organic 
matter. 

Nitrogen  Peroxide.  This  compound  is  liberated  by  heat- 
ing nitrates,  except  those  of  sodium,  potassium,  and  am- 
monium. It  is  a  reddish  brown  gas  and  may  be  easily 
liquefied.  It  parts  with  oxygen  more  readily  than  nitric 
oxide  and  is  a  powerful  oxidizing  agent. 

Nitrous  Oxide  is  the  substance  called  laughing  gas.  Be- 
sides its  characteristic  property  of  an  anaesthetic  it  also  sup- 
ports combustion,  but  in  a  more  limited  manner  than  oxygen. 

The  five  oxides  of  nitrogen  are  an  excellent  illustration 
of  the  law  of  multiple  proportions.  This  law  states  that,  if 
two  elements  unite  in  more  than  one  proportion,  the  quan- 
tities of  one  of  these  elements,  united  with  identical 
amounts  of  the  other,  form  simple  ratios  to  one  another  in 
integral  numbers.  In  the  examples  cited,  the  amounts  of 
the  oxygen  which  are  united  with  a  constant  amount  of 
nitrogen  stand  in  the  ratio  of  1 :  2 :  3 :  4 :  5. 

SUMMARY 

The  atmosphere  is  a  mixture  of  a  number  of  gases.  As  such 
it  is  responsible  for  a  great  many  changes  in  nature  on  account  of  the 
different  properties  of  its  constituents.  Nitrogen  is  the  chief  ingredient 
and  is  important  for  plant  and  animal  life.  Oxygen  is  next  in  abund- 
ance and  it  is  from  this  source  that  the  element  is  obtained  for  the 
common  oxidation  processes.  Water  vapor  is  a  variable  constituent, 
but  is  the  cause  of  many  far-reaching  changes  in  the  earth's  surface. 
Carbon  dioxide  is  also  variable  and  comparatively  small  in  quantity. 


88  CHEMISTRY  OF  THE  FARM  AND  HOME 

It  is  from  this  source,  however,  that  plants  obtain  the  carbon  necessary 
for  their  growth.  The  other  ingredients  of  the  air  are  of  less  importance. 
Nitrogen  is  a  most  important  element.  It  exists  in  both  the 
free  and  the  combined  form  in  nature.  Though  itself  inert,  its  com- 
pounds are  very  active  chemically.  The  common  explosives  either 
contain,  or  are  prepared  by  the  use  of  nitric  acid  or  nitrates.  Am- 
monia and  nitric  acid  are  two  compounds  of  nitrogen  which  have  im- 
portant apphcations  in  commerce  and  industry.  As  nitrogen  is  an 
essential  element  of  plant  and  animal  life,  its  compounds  are  impor- 
tant in  this  connection.  Other  special  uses  of  ammonia  are  as  a  re- 
frigenating  and  cleansing  agent;  of  nitric  acid  and  nitrates,  are  as 
laboratory   reagents  for   oxidizing   reactions. 

QUESTIONS 

1.  Why  are  the  variable  constituents  of  the  atmosphere  found 
in  different  proportions? 

2.  State  the  amount,  source,  and  function  of  the  following  con- 
stituents of  the  atniosphere:  carbon  dioxide,   ammonia,   and  water. 

3.  If  it  is  possible  to  show  that  air  is  made  up  of  two  or  more 
kinds  of  matter,  how  can  the  relative  proportion  of  these  be  proved? 

4.  Is  there  any  difference  between  heating  matter  in  the  air 
and  without  air?     Give  examples. 

5.  When  oxygen  and  nitrogen  are  mixed  in  the  proportion  in 
which  they  exist  in  the  atmosphere,  heat  is  neither  evolved  nor  ab- 
sorbed by  the  process.     What  important  point   does  this  suggest? 

6.  What  is  the  relation  of  the  oxygen  of  the  air  to  respiration? 

7.  Compare  the  breathing  and  burning  processes.  How  are 
they  affected  by  ordinary  air,  by  oxygen  and  by  ammonia? 

8.  In  what  respects   does  oxygen   differ   from   nitrogen? 

9.  How  would  you  distinguish  between  oxygen,  hydrogen,  and 
nitrogen? 

10.  Compare  the  activity  of  nitrogen  with  that  of  its  compounds. 

11.  Discuss  the  circulation  of  the  element  nitrogen   in  nature. 

12.  Why  are  so  few  mineral  compounds  of  nitrogen  found  in 
nature? 

13.  Why  has  it  become  necessary  to  devote  so  much  attention 
to  the  artificial  production  of  fertilizers  containing  nitrogen? 

14.  Predict  the  reaction  to  htmus  of  acid  phosphate,  sour  bread, 
tart  preserves  and  pickles. 

15.  Identify    the    following    materials    from    their    description: 

(a)  A  gas,  lighter  than  the  air,  colorless,  odorless,  tasteless,  does  not 
bum  nor  support  combustion,  active  only  at  very  high  temperatures. 

(b)  A  gas,  heavier  than  the  air,  colorless,  but  has  odor  and  taste,  does 
not  support  combustion  nor  burn,  but  is  active,  forming  a  colored 
gas  when^  coming  in  contact  with  the  air. 


CHAPTER  IV 

SOME  OTHER  NON-METALS 
CHLORINE 

Introduction.  As  an  essential  constituent  of  common 
salt  and  other  compounds  of  importance  to  civilization,  the 
substance  chlorine  is  of  great  value.  It  is  an  exceedingly 
active  substance  and,  therefore,  never  found  free  in  nature. 

Distribution.  Compounds  of  chlorine  are  widely  dis- 
tributed in  nature.  Usually  chlorine  occurs  in  combination 
with  metals  as  chlorides,  of  which  sodium  chloride,  potas- 
sium chloride,  and  magnesium  chloride  are  the  most  abund- 
ant. Nearly  all  salt  water  contains  these  substances,  the 
sodium  chloride  predominating.  Large  salt  beds  are  found 
in  many  parts  of  the  world.  Common  salt,  or  sodium  chlo- 
ride, is  the  chief  compound  and  source  of  chlorine. 

Preparation.    Chlorine  may  be  prepared  in  a  number  of 


Figure  24. — The  preparation  of  chlorine. 


ways.     The  chemical  method  is  essentially  liberating  chlo- 
rine from  hydrochloric  acid  by  an  oxidizing  process.     It  is 

£9 


90  CHEMISTRY  OF  THE  FARM  AND  HOME 

usually  accomplished  by  bringing  hydrochloric  acid  and 
manganese  dioxide  together  in  a  suitable  apparatus,  and 
warming  to  facilitate  the  reaction.  As  the  gas  is  soluble  in 
water  and  heavier  than  the  air,  it  is  collected  by  downward 
displacement  of  air. 

Figure  24  illustrates  the  apparatus  for  preparing  chlorine. 
The  manganese  dioxide  is  placed  in  the  flask  and  hydro- 
chloric acid  added  through  the  thistle  tube.  By  gently 
warming  with  a  burner  the  chlorine  is  liberated  and  may  be 
passed  through  the  bottle  which  contains  water  to  remove 
any  hydrochloric  acid  which  might  contaminate  the  chlo- 
rine. The  latter  is  then  passed  into  a  bottle  which  contains 
only  air.  After  the  bottle  is  filled,  the  gas  can  be  tested  in 
order  to  learn  its  chemical  properties.  The  following  is  the 
equation  for  the  reaction : 

Mn02  +  4  HCl  -^  2  H2O  +  MnClg  +  Clg. 

Chlorine  may  also  be  liberated  by  the  electrolysis  of 
chlorides.  In  the  manufacture  of  caustic  soda  from  sodium 
chloride  chlorine  is  evolved  at  the  anode.  A  great  deal 
of  the  chlorine  required  in  the  chemical  industries  is  made 
in  this  manner.  Electrolysis  of  hydrochloric  acid  solution 
gives  chlorine  at  one  pole  and  hydrogen  at  the  other. 

Physical  Properties.  Chlorine  is  a  greenish  yellow  gas, 
with  a  peculiar,  very  pungent,  suffocating  odor.  It  has  a 
very  irritating  effect  upon  the  throat  and  lungs.  Small 
quantities  produce  all  the  symptoms  of  a  hard  cold  and 
sore  throat.  Larger  quantities  may  cause  serious  and  even 
fatal  action.  It  is  nearly  23^  times  as  heavy  as  the  air, 
1  liter  weighing  3.22  grams.  Three  volumes  of  the  gas 
dissolve  in  one  volume  of  water  under  ordinary  conditions. 
Chlorine  is  readily  liquefied  by  a  pressure  of  six  atmospheres 
at  0°C.  It  forms  a  yellowish  liquid  which  solidifies  at 
-102°C. 

Chemical  Properties.  Chlorine  is  one  of  the  most  active 
of  all  the  chemical  elements.     Its  €ffect  may  be  classified 


SOME  OTHER  NON-METALS  91 

somewhat  as  follows:  (1)  Action  upon  the  metals.  Many 
metals  combine  directly  with  chlorine,  especially  when  hot. 
Gold  and  silver  are  quickly  tarnished  by  the  gas.  Powdered 
antimony  reacts  immediately,  giving  off  much  light  and 
heat.  Both  copper  foil  and  sodium,  if  heated  and  dropped  into 
chlorine,  burn  brilliantly.  Chlorides  of  the  respective  metals 
are  produced  by  all  these  reactions. 

Na2  +  CI2  -^  2  NaCl 

(2)  Action  on  non-metals.  Many  of  the  non-metals  combine 
with  chlorine.     Phosphorus  burns  in  a  current  of  the  gas. 

(3)  Action  on  hydrogen.  Chlorine  has  a  strong  affinity  for 
free  hydrogen,  uniting  with  it  to  form  hydrochloric  acid. 
A  jet  of  burning  hydrogen  continues  to  burn  when  intro- 
duced into  a  jar  of  chlorine,  giving  a  somewhat  luminous 
flame.  A  mixture  of  the  two  gases  explodes  violently  when 
a  spark  is  passed  through  it  or  when  it  is  exposed  to  bright 
sunlight.  In  the  latter  case  it  is  the  light  and  not  the  heat 
which  starts  the  action. 

H2  +  CI2  -^  2  HCl 

(4)  Action  on  substances  containing  hydrogen.  Chlorine 
often  removes  hydrogen  from  compounds  of  the  latter. 
If  chlorine  is  passed  into  hydrogen  sulphide  water,  sulphur 
is  precipitated  and  hydrochloric  acid  is  formed.  Water 
is  decomposed  by  chlorine  in  the  sunlight  and  oxygen  is 
liberated. 

H2O  +  CI2  -^  2  HCl  +  O 

The  attraction  of  chlorine  for  combined  hydrogen 
is  very  strikingly  seen  in  the  action  of  chlorine  upon 
turpentine,  which  is  composed  of  hydrogen  and  car- 
bon. If  a  strip  of  paper  is  moistened  with  warm  turpentine 
and  lowered  into  a  jar  of  chlorine,  there  is  an  immediate 
reaction.  A  black  deposit  of  carbon  is  formed  and  dense 
fumes  of  hydrochloric  acid  appear.  (5)  Bleaching  action. 
When  colored  substances  are  moistened  with  water  and 
exposed  to  the  action  of  chlorine,  the  chlorine  reacts  with 


93 


CHEMISTRY  OF  THE  FARM  AND  HOME 


the  water  as  stated  above  and  liberates  oxygen.  This 
oxygen  is  very  active,  far  more  active  than  pure  oxygen, 
and  is  said  to  be  in  the  nascent  state.  The  oxygen  oxidizes 
the  color  substance  and  converts  it  to  a  colorless  compound. 
That  the  moisture  is  necessary  for  the  reaction  is  proved 
by  subjecting  colored  materials  to  dry  chlorine  gas.  No 
changes    follow.     (6)     Disinfecting    action.     Chlorine    has 

marked      germicidal      properties. 

Both  the  free  element  and  com- 
pounds from  which  it  can  be 
readily  liberated  are  used  as  dis- 
infectants. Chlorine  water  j  sl  solu- 
tion of  chlorine  in  water,  is  a 
powerful  bleaching  agent  and 
disinfectant.  Chloride  of  lime, 
bleaching  powder,  is  also  a  bleach- 
ing and  disinfecting  agent. 

In  Figure  25  is  shown  an  ar- 
rangement for  the  purification  of 
water  by  liquid  chlorine.  The  two 
cylinders  contain  the  liquid  which 
under  reduced  pressure  becomes 
a  gas.  The  latter  is  conducted 
up  through  a  tube  made  of  resist- 
ant stoneware.  In  this  way  it 
comes  in  contact  with  a  very 
small  amount  of  water  in  the 
form  of  a  spray.  The  chlorine 
water  produced  passes  out  of  the  bottom  of  the  tower 
and  is  conducted  to  the  water  or  sewage  to  be  treated. 
It  has  an  instantaneous  action  upon  bacteria  and  other 
oxidizable  materials.  Water  thus  treated  is  said  to  have 
no  disagreeable  odor  or  taste  and  the  process  is  claimed  to 
be  far  superior  to  the  ordinary  hypochlorite  or  bleaching 
powder  method. 


Figure  25 

water  by  chlorine. 


The  purification  of 
;hl 


SOME  OTHER  NON-METALS^  93 

Hydrochloric  Acid  (HCl).  This  substance  is  prepared  by 
the  action  of  sulphuric  acid  upon  sodium  chloride.  The  dry 
salt  is  placed  in  a  flask  with  a  funnel  tube  and  an  exit  tube,  the 
sulphuric  acid  added  and  the  flask  gently  warmed.  The 
hydrochloric  acid  is  rapidly  given  off  and  collected  in  bottles 
by  displacement  of  air.  The  same  apparatus  (Figure  24) 
that  is  used  for  the  preparation  of  chlorine  can  be  utilized 
for  making  hydrochloric  acid.  The  wash  bottle  should, 
however,  be  omitted  from  the  arrangement.  The  equation 
for  the  reaction    is 

2  NaCl  +  H2SO4  -^  2  HCl  +  Na2S04. 
This  process  is  one  stage  of  the  old  Leblanc  method  for 
preparing  sodium  carbonate  from  sodium  chloride.  Another 
method  by  which  hydrochloric  acid  may  be  prepared  is  the 
combining  of  hydrogen  and  chlorine  gases  by  an  electric 
spark  or  a  flame. 

Physical  Properties.  Hydrochloric  acid  is  a  colorless 
gas,  has  a  sour,  biting  taste,  and  a  pungent  odor.  It  causes 
an  irritating  effect  upon  the  mucous  membranes  of  the  eyes, 
nose,  and  throat.  It  is  heavier  than  the  air,  1.26  density, 
and  is  very  soluble  in  water.  In  fact,  it  fumes  in  the  air, 
since  it  condenses  atmospheric  water  to  drops.  The  fumes 
are  really  minute  droplets  of  an  aqueous  solution  of  hydro- 
chloric acid  gas.  One  volume  of  water  dissolves  about  500 
volumes  of  hydrochloric  acid  gas  under  ordinary  conditions. 
The  most  concentrated  solution  of  hydrochloric  acid  has  a 
density  of  1.20  and  contains  40%  hydrochloric  acid  gas. 
The  pure  acid  is  colorless,  but  the  commercial  acid,  muriatic 
acid,  is  yellow  on  account  of  the  presence  of  impurities, 
such  as  chloride  of  iron.  On  boiling  a  solution  of  hydro- 
chloric acid,  the  gas  will  escape  until  the  liquid  has  20%  by 
weight  of  hydrochloric  acid  gas.  If  the  solution  is  weaker 
than  this,  water  is  driven  off  by  boiling  until  the  concentra- 
tion of  20%  is  reached.  In  both  cases  the  liquid  remaining 
distills  over  unchanged  at  that  point.     Hydrochloric  acid 


94  CHEMISTRY  OF  THE  FARM  AND  HOME 

gas  is  liquefied  at  0°C.  under  a  pressure  of  28  atmospheres. 
A  colorless  liquid  is  formed  which  is  not  very  active  chemi- 
cally. It  boils  at  —80°  and  soUdifies  at  — 113°.  The  water 
solution  of  hydrochloric  acid  is  the  usual  form  in  which  the 
compound  is  met  in  the  laboratory.  It  is  far  more  con- 
venient and  more  active  than  the  gaseous  form. 

Chemical  Properties.  Some  of  the  most  important 
chemical  properties  of  hydrochloric  acid  are  the  following: 
(1)  Action  as  an  acid.  The  water  solution  of  hydrochloric 
acid  has  strong  acid  properties.  In  fact,  it  is  one  of  the 
strongest  acids.  It  reacts  with  bases  to  form  chlorides  and 
water.  It  is  a  common  laboratory  reagent.  (2)  Relation 
to  combustion.  Hydrochloric  acid  is  not  readily  decomposed, 
it  does  not  burn,  nor  does  it  support  burning.  (3)  Action 
with  oxidizing  agents.  Hydrochloric  acid  is  oxidized  under 
some  conditions  with  the  liberation  of  chlorine.  The 
principle  of  this  reaction  has  already  been  cited  under  the 
preparation  of  chlorine.  When  nitric  acid  and  hydro- 
chloric acid  are  mixed,  the  nitric  acid  oxidizes  the  hydro- 
chloric acid,  liberating  chlorine  and  some  other  substances. 
This  mixture  is  called  aqua  regia  and  is  more  powerful  than 
either  acid  separately.  Its  strength  is  due  to  the  action  of 
the  nascent  chlorine  it  liberates. 

3  HCI+HNO3  -^  CI2  +  NOCl  +  2  H2O 

In  the  human  stomach  there  is  found  a  0.3%  solution 
of  hydrochloric  acid  which  aids  in  the  digestion  of  the  food. 

Chlorides.  The  chlorides  are  salts  of  hydrochloric 
acid.  All  the  metals  form  chlorides  and  many  of  them  are 
very  important  compounds.  Some  of  them  are  found  in 
nature.  All  of  them  can  be  prepared  by  the  general  method 
of  preparing  salts. 

Other  Compounds  of  Chlorine.  Two  oxides  of  chlorine 
are  known.  This  element  combines  with  hydrogen  and 
oxygen  to  form  four  different  acids.  They  are  all  unstable 
and  most  of  them  cannot  be  prepared  in  the  pure  form. 


SOME  OTHER  NON-METALS  95 

Their  salts  are,  however,  easily  prepared  and  some  of 
them  are  very  important  for  laboratory  and  commercial 
purposes. 

Calcium  Hypochlorite.  One  example  of  such  a  com- 
pound is  calcium  hypochlorite,  CaCl(OCl),  often  called 
bleaching  powder,  and  incorrectly  called  chloride  of  lime. 
This  substance  is  manufactured  by  the  action  of  chlorine 
upon  lime.  The  lime  is  carefully  slaked  with  water  to  form 
calcium  hydroxide  and  this  is  placed  in  a  large  absorption 
chamber.  The  chlorine,  generated  by  the  electrolysis  of 
sodium  chloride,  is  passed  in  at  the  top  of  the  chamber 
and  absorbed  by  the  lime  as  it  settles  to  the  bottom  of  the 
chamber.  Bleaching  powder  is  a  yellowish  white  sub- 
stance having  a  peculiar  odor,  which  resembles  that  of 
chlorine.  Upon  exposure  to  the  air  it  absorbs  carbon  diox- 
ide and  loses  part  of  its  chlorine.  Acids  liberate  chlorine 
from  the  powder,  the  amount  being  from  30  to  38%  in 
a  good  quahty.  When  this  reaction  takes  place  in  contact 
with  cotton  cloth,  for  example,  the  chlorine  liberated  has  a 
powerful  indirect  oxidizing  and  bleaching  effect  upon  the 
coloring  matter  or  impurities  of  the  cotton.  Bleaching 
powder  is,  therefore,  a  very  important  chemical  used  in 
the  textile  industry. 

The  Halogens.  There  are  three  other  elements  which 
resemble  chlorine  in  a  general  way  in  their  properties.  These 
elements  are  fluorine,  bromine,  and  iodine.  Because  the 
compounds  of  three  of  them  are  found  in  sea  water,  the  name 
halogen,  or  producer  of  sea  salts,  is  applied  to  the  group. 
None  of  these  elements  occurs  free  in  nature.  Their  physi- 
cal properties  change  gradually  with  increase  of  atomic 
weight.  Their  melting  points  and  boiling  points  increase, 
their  color  grows  more  intense,  and  their  form  changes 
from  gas  to  liquid  to  solid.  Their  chemical  properties, 
though,  seem  to  decrease  with  increase  of  atomic  weight. 
That  is,  the  activity  of  fluorine  is  far  greater  than  that  of 


96       CHEMISTRY  OF  THE  FARM  AND  HOME 

iodine.  This  is  shown  very  strikingly  in  the  attraction  of 
these  elements  for  hydrogen.  Fluorine  combines  with 
hydrogen  explosively  and  abstracts  hydrogen  from  its 
compounds  actively.  Iodine  on  the  other  hand  does  neither 
readily.  While  all  these  elements  have  important  uses, 
chlorine  is  by  far  the  most  valuable  to  mankind.  The 
chemistry  of  the  other  three  is  similar  to  that  of  chlorine, 
varying  chiefly  in  degree. 

SULPHUR 

Introduction.  Sulphur  has  been  known  from  the  earli- 
est times,  since  it  is  widely  distributed  and  occurs  in  large 
quantities  in  the  uncombined  form.  Sulphur  forms  a  number 
of  important  compounds,  notably  sulphuric  acid,  which  is 
of  great  usefulness  in  numberless  chemical  industries. 

Distribution.  Sulphur  occurs  in  nature  in  both  the  free 
and  the  combined  forms.  In  the  free  condition  it  is  ob- 
tained chiefly  from  Sicily,  Mexico,  Iceland,  and  Louisiana, 
where  it  is  found  largely  in  volcanic  and  spring  deposits. 
In  the  combined  form  sulphur  exists  as  sulphates  and  sul- 
phides of  many  metals,  as  of  iron,  copper,  calcium,  and 
barium.  Besides  these  minerals  it  is  also  a  constituent  of 
many  animal  and  vegetable  substances.  For  example,  the 
yolk  of  an  egg  and  plants  of  the  cruciferae  family  contain 
large  amounts  of  sulphur  in  combination. 

Preparation.  Natural  sulphur  is  usually  found  mixed 
with  much  earthy  material,  from  which  it  must  be  separated 
to  prepare  it  for  the  market.  The  purification  process  con- 
sists of  two  stages.  It  is  first  heated  on  an  inclined  surface 
whereby  the  sulphur  melts  and  flows  away,  leaving  the 
impurities  behind.  Second,  the  partiafly  purified  sulphur 
is  distilled  from  large  iron  retorts  and  is  thus  separated 
from  less  volatile  impurities.  The  sulphur  vapor  is  con- 
ducted into  a  cooling  chamber  of  brickwork  where  it  con- 
denses.    The  fine  crystalline  powder  first  formed  is  called 


^^OME  OTHER  NON-METALS  97 

flowers  of  sulphur.  As  the  temperature  of  the  condensing 
chamber  increases  the  sulphur  collects  as  a  liquid  in  it  and 
is  drawn  off  into  cylindrical  molds,  the  product  being  called 
roll  sulphur  or  brimstone. 

Physical  Properties.  Sulphur  exists  in  several  different 
physical  forms,  two  crystalUne  and  two  amorphous.  While 
some  of  their  properties  are  common  to  all  the  forms,  there 
are  a  number  of  properties  that  differ  considerably.  (1) 
Ordinary  or  rhombic  sulphur  is  the  natural  and  most  stable 
form.  All  other  forms  revert  to  this  at  ordinary  tempera- 
tures. It  is  yellow,  odorless,  tasteless,  and  melts  at  114.5°C. 
It  has  a  specific  gravity  of  2.06,  is  very  soluble  in  carbon 
disulphide,  but  is  insoluble  in  water.  Roll  sulphur  or  brim- 
stone is  composed  of  minute  rhombic  crystals.  Above 
96°C.  rhombic  sulphur  changes  to  prismatic  sulphur.  (2) 
Prismatic  or  monoclinic  sulphur  is  formed  by  the  slow  cool- 
ing of  melted  sulphur.  As  soon  as  a  crust  forms,  it  is  broken 
and  the  Uquid  is  poured  off.  The  crystals  are  long,  almost 
colorless  needles,  that  melt  at  119°C.,  dissolve  in  carbon 
disulphide,  and  have  a  specific  gravity  of  1.96.  If  kept 
below  96°C.,  they  change  in  a  few  days  to  the  rhombic 
form  with  evolution  of  heat.  The  temperature  96°  is  called 
the  transition  point  of  sulphur. 

Two  varieties  of  amorphous  or  non-crystalline  sulphur 
can  readily  be  obtained.  Plastic  sulphur  is  formed  by  heat- 
ing ordinary  sulphur  and  cooling  it  very  suddenly.  If  the 
boiling  sulphur  is  chilled  suddenly  by  passing  it  into  cold 
water,  the  product  becomes  an  elastic,  gummy,  and  non- 
crystallized  substance.  This  becomes  hard  and  brittle 
after  several  days  and  consists  of  rhombic  sulphur  which 
is  soluble  in  carbon  disulphide  and  an  amorphous  vari- 
ety which  is  insoluble  in  carbon  disulphide.  Amorphous 
sulphur  is  the  hardened  form  of  the  dark,  viscous  liquid. 
It  was  not  given  time  to  crystallize  hke  the  ordinary  form 
on  account  of  the  sudden  cooling.    When  kept  below  96°C. 

7— 


98       CHEMISTRY  OF  THE  FARM  AND  HOME 

it  changes  slowly  into  rhombic  sulphur  with  evolution  of 
heat.  Flowers  of  sulphur  have  a  nucleus  of  rhombic  crystals 
and  an  amorphous  covering.  These  amorphous  particles 
are  insoluble  in  carbon  disulphide  and  are  left  as  a  white 
residue  when  flowers  of  sulphur  are  treated  with  that  chemi- 
cal. Hence  the  name  white  sulphur  is  applied  to  the  other 
amorphous  variety. 

The  following  changes  ordinarily  take  place  when  sul- 
phur is  heated.  At  114.5°C.  ordinary  sulphur  becomes  a 
thin  yellow  or  straw  colored  liquid.  As  the  temperature  is 
raised  above  1 60°C.  this  liquid  becomes  darker  and  thicker. 
At  230°C.  it  is  almost  black  and  is  so  thick  that  it  can  hardly 
be  poured.  At  higher  temperatures,  above  300°C.,  it  be- 
comes thin  again  and  at  445°C.  it  boils,  giving  a  yellowish 
brown  vapor.  If  allowed  to  cool  slowly,  these  changes  are 
repeated,  but  in  the  reverse  order  until  ordinary  sulphur 
is  finally  obtained. 

Chemical  Properties.  Sulphur  unites  directly  with  many 
elements,  especially  the  metals.  These  reactions  occur  more 
readily  with  increase  of  temperature,  though  there  are  some 
common  illustrations  of  the  action  under  ordinary  condi- 
tions. Mercury  combines  with  sulphur  when  the  two  are 
simply  rubbed  together  in  a  mortar.  Copper  foil  burns  in 
sulphur  vapor  giving  copper  sulphide.  Silverware  may  be 
blackened  by  the  sulphur  in  eggs  or  by  the  sulphur  com- 
pounds in  illuminating  gas.  Silver  coins  which  are  carried 
in  pockets  are  colored  by  the  sulphur  of  the  perspiration. 

Sulphur  unites  readily  with  oxygen  if  heated,  the  action 
beginning  at  260°C.  It  burns  with  a  pale  blue  flame,  form- 
ing sulphur  dioxide.  Small  quantities  of  sulphur  trioxide 
may  also  be  produced  by  the  process.  Sulphur  dioxide  is 
an  invisible  gas  which  is  characteristic  of  the  well  known 
odor  of  burning  sulphur. 

Uses  of  Sulphur.  Sulphur  has  many  important  com- 
mercial uses.     Rubber  goods  and  vulcanite  are  made  by 


SOME  OTHER  NON-METALS 


99 


heating  together  caoutchouc  and  sulphur.  Match  tips  of 
the  older  style  contain  sulphur.  Gunpowder  is  a  mixture 
of  carbon,  sulphur,  and  saltpeter.  Sulphur  is  used  in  the 
production  of  sulphur  dioxide  which  is  extensively  used  for 
bleaching  and  as  a  germicide.  Sulphur  is  being  used  more 
and  more  as  a  material  for  controlling  plant  diseases,  and, 
to  a  lesser  extent,  plant  insect  pests.  Sulphuric  acid,  which 
is  probably  the  most  important  chemical  manufactured,  is 
prepared  from  sulphur. 

Compounds  of  Sulphur.  Many  compounds  of  import- 
ance to  agriculture  and  commerce  contain  sulphur.  The 
sulphides,  next  to  the  oxides,  are  the  most  common  ores  of 
the  metals.  Sulphur  forms  two  important  oxides,  and  in 
combination  with  hydrogen  and  oxygen,  a  number  of  acids. 
Hydrogen  sulphide,  hydrosulphuric  acid,  H2S-  This 
compound  is  a  colorless  gas,  with  a  very  disagreeable 
odor,  and  a  weak  disagreeable  taste.  In  the  pure  form  it 
^^^^=z^  acts  as  a    violent  poison,   and  even  when 

diluted  largely  with  air  produces  headache, 
dizziness,  and  nausea.  It  is  formed  natur- 
ally by  the  decomposition  of  organic  matter 
which  contains  sulphur.  Since  eggs  contain 
this  element  and  give  rise  to  this  gas  when 
decaying,  it  is  often  said  to  be  the  gas  with 
the  odor  of  rotten  eggs.  Natural  sulphur 
waters  and  the  vapor  issuing  from  volcanoes 
contain  hydrogen  sulphide. 

Hydrogen  sulphide  is  prepared  in  the 
laboratory  by  treating  ferrous  sulphide  with 
dilute  hydrochloric   or   sulphuric    acids.     A 

Figure  26 — Gener-  •       ,      ,  r  i  <•  i       i 

ator  for  hydrogen  convemeut  type  oi  generator  tor  hydrogen 
sulphide  is  shown  in  Figure  26.  The  inner 
tube  contains  the  ferrous  sulphide  and  is  lowered  into  the 
bottle  containing  the  acid.  By  turning  the  stopcock  in 
the  delivery  tube  the  acid  rises  and  attacks  the   sulphide 


^-> 


a 


II 

1 

1 

100      CHEMISTRY  OF  THE  FARM  AND  HOME 

of  iron.  The  hydrogen  sulphide  is  forced  over  by  the  pres- 
sure and  can  be  collected  in  bottles  by  the  downward 
displacement  of  air.  Or,  if  it  is  desired  to  use  the  water 
solution  of  the  substance,  the  gas  can  be  passed  directly  into 
the  water  until  the  latter  is  saturated  with  it.  The  equation 
follows: 

FeS     +     2HC1     -^     H2S     +     FeCl2 

The  specific  gravity  of  hydrogen  sulphide  gas  is  1.18. 
Three  volumes  are  soluble  in  one  volume  of  water  at  ordinary 
temperatures.  A  jet  of  the  gas  completely  burns  in  plenty 
of  air,  forming  water  and  sulphur  dioxide.  If  the  air  supply 
is  limited,  however,  only  the  hydrogen  of  the  compound 
burns.  Hydrogen  sulphide  is  easily  broken  down  by  heat 
into  its  elements.  The  aqueous  solution  is  even  decomposed 
by  light  and  by  the  oxygen  of  the  air  into  sulphur  and  water. 
Oxidizing  agents  affect  the  aqueous  solution  in  the  same  way. 
On  account  of  these  facts,  hydrogen  sulphide  is  a  strong 
reducing  agent,  taking  oxygen  away  from  many  substances 
which  contain  it.  It  is  also  a  weak  acid.  Its  water  solution 
turns  blue  litmus  red  and  neutralizes  bases,  forming  salts, 
called  sulphides.  It  acts  towards  metals  much  as  water. 
For  example,  if  each  of  these  substances  is  passed  over  heated 
iron  in  a  tube,  in  the  case  of  water  iron  oxide  is  formed  and 
hydrogen  is  liberated;  in  the  case  of  hydrogen  sulphide  iron 
sulphide  is  formed  and  hydrogen  is  liberated. 

Most  of  the  sulphides  are  insoluble  in  water  and  some 
are  insoluble  in  acids.  On  account  of  this  difference  in  the 
properties  of  the  metallic  sulphides,  it  is  possible  to  separate 
the  metals  in  the  laboratory.  Hydrogen  sulphide  is  a  con- 
venient reagent  for  this  purpose,  the  gas  being  passed  directly 
into  water  solutions  of  the  metallic  compounds.  This  is 
one  of  the  principal  uses  of  hydrogen  sulphide. 
CUSO4  +  H2S  ->  CuS  +  H2SO4 

Carbon  Bisulphide,  CS2.  This  substance  is  formed  by 
the  direct  union  of  carbon  and  sulphur.     It  can  be  affected 


SOME  OTHER /N<^N-m'TA0:  >/^  i/j^  101 


by  passing  sulphur  vapor  over  hot  charcoal,  or  an  electric  fur- 
nace may  be  utilized  to  bring  about  the  result.  Pure  car- 
bon disulphide  is  a  colorless  liquid,  having  a  pleasant  odor. 
Commercial  carbon  disulphide  is  often  yellow  and  has  a 
very  disagreeable  odor.  It  is  very  inflammable,  boiling  at 
47°C.  and  has  a  specific  gravity  of  1.27.  The  chief  use  of 
the  compound  is  as  a  solvent  for  sulphur,  caoutchouc,  phos- 
phorus, iodine,  resins,  and  waxes.  It  is  also  used  as  an 
insecticide  and  for  killing  rodents. 

Sulphur  dioxide,  SO  2.  Sulphur  dioxide  is  the  gas  pro- 
duced by  burning  sulphur  in  air  or  in  oxygen.  It  can  also 
be   prepared   by   oxidizing   or   roasting   certain   sulphides, 


(^=&^ 


Figure  27. —  The  preparation  of  liquid  sulphur  dioxide. 

notably  the  sulphide  of  iron  called  iron  pyrites.  This  is 
one  of  the  commercial  methods  used  in  the  manufacture  of 
sulphuric  acid.  Sulphur  dioxide  is  commonly  prepared  in 
the  laboratory  by  one  of  the  following  methods:  by  the 
action  of  acids  upon  sulphites,  and  by  heating  concentrated 
sulphuric  acid  with  copper.  In  the  latter  process  the  sulphur 
dioxide  is  given  off  as  a  gas  and  copper  sulphate  and  water 
are  the  other  products.  Sulphur  dioxide  occurs  in  nature 
in  the  gases  issuing  from  volcanoes  and  dissolved  in  the  water 
of  many  springs. 

Physical  Properties.     Sulphur  dioxide  is  a  colorless  gas, 
with  a  peculiar,  irritating  odor,  and  a  disagreeable  taste. 


102  ^Q^EMlJili:f:^li^  i^pj  FARM  AND  HOME 

It  is  2.2  times  as  heavy  as  the  air  and  very  soluble  in  water, 
80  volumes  dissolving  in  1  volume  of  water  at  0°C.  Sul- 
phur dioxide  can  be  obtained  in  the  liquid  form  by  passing 
it  through  a  condensing  tube  surrounded  by  a  freezing  mix- 
ure  of  ice  and  salt.  If  a  current  of  air  is  passed  over 
sulphur  heated  in  the  bulb  A  and  the  products  of  the 
reaction  are  then  cooled  in  the  bulb  B,  the  sulphur  dioxide 
may  be  liquefied  and  collected.  (See  Figure  27.)  Liquid 
sulphur  dioxide  is  colorless  and  boils  at  —  8°C.  Since  the 
evaporation  of  this  substance  absorbs  much  heat,  it  is 
often  used  as  a  refrigerating  agent.  Liquid  sulphur  dioxide 
can  be  purchased  in  strong  bottles  or  sealed  tins. 

Chemical  Properties.  Sulphur  dioxide  is  an  active 
substance  chemically.  It  combines  with  oxygen,  both  free 
and  combined.  Its  most  characteristic  property  is  its 
ability  to  unite  with  water  to  form  sulphurous  acid.  Sul- 
phur dioxide  is  a  very  powerful  bleaching  and  disinfecting 
agent.  It  is  extremely  valuable  for  bleaching  silks,  woolens, 
laces  and  straws  which  might  be  injured  by  chlorine.  The 
sulphur  dioxide  probably  combines  with  the  coloring  matter 
of  these  fabrics  forming  colorless  compounds.  The  bleach- 
ing effect,  however,  may  disappear  in  time.  Sulphur 
dioxide  has  even  been  used  to  bleach  and  preserve  food 
products,  such  as  molasses,  dried  fruits,  etc.;  but  this  par- 
ticular use  is  restricted  by  the  food  laws  of  many  states. 
Sulphur  dioxide  is  readily  oxidized  to  sulphur  trioxide  and 
is  in  this  way  important  for  the  preparation  of  sulphuric 
acid.  The  water  solution  of  sulphur  dioxide  has  the  pro- 
perties of  a  weak  acid,  and  is  called  sulphurous  acid.  This 
substance  is  oxidized  to  sulphuric  acid  slowly  by  the  air,  but 
rapidly  by  oxidizing  agents.  When  neutralized  by  bases, 
sulphurous  acid  forms  a  series  of  salts  called  sulphites. 
These  also  oxidize  readily.  Sulphurous  acid  has  marked 
antiseptic  properties  and  has  the  power  of  arresting  fer- 
mentation.    It  is,  therefore,  used  as  a  preservative. 


SOME  OTHER  NON-METALS  103 

Sulphur  Trioxide,  SO3.  Sulphur  trioxide  is  a  colorless 
Hquid  above  15°C.  and  boils  at  46°C.  Below  15°C.  it  is 
a  white  crystalline  solid.  In  the  air  sulphur  trioxide  gives 
off  dense  choking  fumes.  It  reacts  with  water  violently- 
causing  intense  heat  and  a  hissing  sound.  Sulphur  trioxide 
is  prepared  by  oxidation  of  sulphur  dioxide.  A  small 
amount  may  be  formed  by  the  simple  burning  of  sulphur  in 
the  air  or  oxygen.  When  sulphur  dioxide  and  oxygen 
are  heated  together  some  sulphur  trioxide  may  be  formed. 
The  reaction  is  practically  complete  when  a  catalytic  agent, 
as  platinized  asbestos,  is  used. 

The  term  catalytic,  or  contact  agent,  is  applied  to  a 
substance  which  aids  a  chemical  reaction  in  some  way. 
The  process  is  called  catalysis,  or  contact  action.  Ap- 
parently by  its  mere  presence  the  catalytic  agent  increases 
the  speed  of  a  chemical  change  without  itself  suffering 
any  permanent  change.  There  are  numerous  examples 
of  catalysis  in  chemistry.  The  effect  of  manganese  dioxide 
upon  potassium  chlorate  in  the  preparation  of  oxygen  is 
a  notable  one.     Do  you  recall  just  what  this  action  is? 

This  is  the  principle  of  the  contact  process  for  the  manu- 
facture of  sulphuric  acid.  The  gases  are  mixed,  heated  and 
passed  into  the  contact  chamber  where  the  sulphur  trioxide 
is  produced.  This  is  then  absorbed  in  water  or  dilute  sul- 
phuric acid,  when  it  combines  with  the  water  and  gives  the 
acid.  In  the  older  or  chamber  process  the  oxidation  of  the 
sulphur  dioxide  takes  place  in  the  presence  of  water  vapor. 
Steam,  air,  sulphur  dioxide,  and  oxides  of  nitrogen  are  all 
used  in  this  method.  The  nitric  acid  used  in  the  process 
furnishes  the  nitric  oxide,  NO,  which  is  successively  oxidized 
by  the  air  to  nitrogen  peroxide,  NO2,  and  reduced  by  the 
sulphur  dioxide  to  nitric  oxide,  NO,  continuously.  The 
oxidation  of  the  sulphur  dioxide  to  sulphur  trioxide  is  really 
caused  by  the  oxygen  of  the  air,  but  the  nitric  oxide  is  the 
catalytic  agent  or  carrier  necessary.     The  sulphuric  acid 


104  CHEMISTRY  OF  THE  FARM  AND  HOME 

made  by  this  process  is  dilute,  containing  about  35%  water. 
It  is  concentrated  by  evaporation,  first  in  leaden  pans, 
then  in  cast  iron  pans,  and  finally  in  glass,  porcelain,  or 
platinum  vessels.  The  equation  for  both  of  these  reactions  is 
SO3+H2O  ->  H2SO4. 

Sulphuric  Acid,  H2SO4.  Properties.  Sulphuric  acid  is  a 
thick,  oily,  colorless  Hquid,  with  a  specific  gravity  of  1.84. 
Ordinary  concentrated  acid  contains  about  2%  water  and 
boils  at  338°C.  When  diluted  with  water,  much  heat  is 
evolved.  To  avoid  the  boiling  and  possible  spattering  of 
the  liquid,  the  concentrated  acid  is  always  slowly  added  to 
the  water  in  a  small  stream.     Never  pour  water  into  the  acid. 

Sulphuric  acid  possesses  a  number  of  chemical  proper- 
ties which  constitute  it  one  of  the  most  important  chemical 
substances  known.  In  dilute  solution  it  has  the  properties 
typical  of  an  acid.  With  oxides  and  bases  it  forms  a  series 
of  salts  call.ed  sulphates.  Sulphuric  acid  contains  a  large 
amount  of  oxygen  and  is  a  good  oxidizing  agent.  As  it  is 
made  by  the  oxidation  of  sulphur  dioxide  to  sulphur  trioxide 
the  reduction  of  the  sulphur  trioxide  to  sulphur  dioxide  is 
possible.  This  is  accomplished  by  simply  boiling  or  heating 
the  acid  in  contact  with  sulphur,  carbon,  or  copper.  The 
action  of  the  acid  upon  metals  depends  considerably  upon 
the  concentration  of  the  acid.  The  dilute  acid  dissolves 
many  metals,  forming  sulphates  and  liberating  hydrogen. 
The  concentrated  acid,  as  j  ust  shown,  in  contact  with  metals 
usually  liberates  sulphur  dioxide,  because  the  hydrogen 
first  produced  reacts  with  the  sulphuric  acid  itself  and  forms 
sulphurous  acid,  then  sulphur  dioxide  and  water. 

Sulphuric  acid  has  a  very  strong  attraction  for  water. 
On  account  of  this  property  it  is  used  as  a  drying  agent  in  the 
chemical  laboratory.  This  dehydrating  power  not  only 
applies  to  free  water  but  also  to  the  elements  of  water  when 
combined  with  other  elements,  such  as  carbon.  The  action 
can  be  very  readily  shown  by  dipping  a  piece  of  wood  into 


SOME  OTHER  NON-METALS  105 

the  strong  acid.  The  wood  chars,  because  the  acid  ab- 
stracts the  hydrogen  and  oxygen  and  leaves  the  carbon. 
The  boiHng  point  of  sulphuric  acid  is  higher  than  that  of 
almost  any  common  acid.  It  is,  therefore,  largely  used  in 
the  preparation  of  other  acids. 

Uses  of  Sulphuric  Acid.  This  chemical,  sometimes 
called  oil  of  vitriol,  is  made  in  enormous  quantities  and  is 
without  doubt  the  most  important  artificial  substance  known 
to  civilized  man.  Some  of  the  valuable  materials  manu- 
factured by  the  aid  of  the  compound  are  nitroglycerine, 
nitric  acid,  hydrochloric  acid,  and  coal  tar  products.  Some 
important  processes  in  which  sulphuric  acid  is  used  are  the 
refining  of  petroleum,  the  preparation  of  glucose,  the  manu- 
facture of  sodium  carbonate  by  the  Leblanc  process,  and 
the  conversion  of  insoluble  phosphates  into  available  phos- 
phate fertilizers.  The  use  of  sulphur  as  a  fungicide  may  de- 
pend upon  its  slow  oxidation  by  atmospheric  means  into  sul- 
phuric acid  which  destroys  the  mildew  or  other  plant  pest. 

Sulphates.  The  salts  of  sulphuric  acid  are  called  sul- 
phates. A  number  of  these  compounds  have  commercial 
uses,  for  example,  copper  sulphate,  or  blue  vitriol,  ferrous 
sulphate,  or  green  vitriol,  and  magnesium  sulphate,  or 
Epsom  salts.  Many  sulphates  are  found  in  nature,  as 
gypsum,  or  calcium  sulphate,  and  barytes,  or  barium  sul- 
phate. Since  sulphuric  acid  is  dibasic,  there  are  both 
normal  and  acid  salts.  They  can  easily  be  prepared  by  a 
number  of  methods.  The  test  for  soluble  sulphates  is  by 
means  of  barium  chloride,  in  the  presence  of  hydrochloric 
acid.  Under  these  conditions  a  permanent  white  precipi- 
tate indicates  sulphates. 

PHOSPHORUS 

Introduction.  In  a  general  way  phosphorus  resembles 
nitrogen  in  its  properties.  Both  are  non-metals,  both  have 
the  same  valencies,  and  both  form  a  similar  series  of  com- 
pounds, though  the  behavior  of  these  compounds  is  often 


106 


CHEMISTRY  OF  THE  FARM  AND  HOME 


very  different.  Phosphorus  is  an  element  which  has  many 
uses  in  civiUzed  Hfe.  It  is  of  the  greatest  interest  in  agricul- 
ture, as  it  is  probably  the  most  important  element  to  con- 
sider in  connection  with  the  maintenance  of  soil  fertility. 

Distribution.  Phosphorus  never  occurs  in  nature  in  the 
free  form,  on  account  of  its  great  chemical  activity.  It  is 
the  chief  mineral  constituent  of  the  bones  and  teeth  of 
animals,  and  is  also  found  in  other  portions  of  the  body,  as 
the  nerves  and  the  brain.  Phosphorus  is  a  very  important 
ingredient  of  the  protoplasm  of  plants  and,  as  the  latter  near 
maturity,  the  greater  portion  of  this  element  is  found  in 
the  seed  or  tuber.  It  occurs  in  soils  to  a  certain  extent,  the 
amount  depending  upon  the  particular  formation  of  the 
soil  in  question.  The  greatest  source  of  phosphorus  is  in 
the  natural  deposits  of  calcium  phosphate  which  are  quite 
abundant  and  widely  distributed.  Some  of  the  chief  depos- 
its occur  in  the  southeastern  part  of  the  United  States, 
Utah  and  Wyoming.  Other  deposits  are  reported  in  Russia 
and  North  Africa.  Some  of  these  phosphates  are  phos- 
phorite and  apatite.    The  former  is  found  in  beds  of  fossil 

bones,  the  other  is  com- 
posed of  calcium  phosphate 
and  calcium  fluoride.  Such 
rock  phosphates  are  very 
valuable  and  are  exten- 
sively mined  for  use  as 
fertilizers. 

Preparation.     P  h  o  s  - 

phorus    is    manufactured 

from  bone  ash  or  a  pure 

mineral  phosphate  by  re- 

oo    rrn.  *  ^       t  X.     u         moving  the   calcium  and 

Figvire  28. — The  manufacture  of  phosphorus.         '^        &  ... 

oxygen  with  which  it  is 
combined.  This  is  accomplished  by  heating  the  phosphate 
with  sand  and  carbon  in  an  electric  furnace.      The  sand, 


^^^ 


SOME  OTHER  NON-METALS  107 

silica,  combines  with  the  hme  forming  a  glassy  slag,  cal- 
cium silicate,  which  may  be  removed  by  a  proper  opening 
in  the  lower  part  of  the  apparatus.  The  carbon  combines 
with  the  oxygen  and  passes  off  as  a  gas,  carbon  monoxide. 
The  phosphorus  vapor  is  passed  out  of  an  opening  (c)  in 
the  upper  part  of  the  furnace  and  is  condensed  under  water. 
This  phosphorus  is  further  purified  by  distillation.  See 
Figure  28. 

Physical  Properties.  Pure  phosphorus  is  pale  yellow  in 
color,  translucent  and  quite  waxy  in  appearance.  It  melts 
at  44°  and  boils  at  269°C.  It  is  quite  soft,  can  easily  be  cut 
with  a  knife  and  cast  into  any  convenient  form  under  slightly 
warm  water.  //  is  always  kept  under  water  for  storage  or 
for  handlings  as  it  is  very  inflammable.  It  is  insoluble  in 
water,  but  is  very  soluble  in  carbon  disulphide  and  some 
other  liquids.     Its  density  is  1.8. 

Chemical  Properties.  When  exposed  to  the  air,  phos- 
phorus slowly  oxidizes  and  emits  a  faint  glow  or  phosphor- 
escence. The  heat  of  the  room  may  aid  this  oxidation 
and  easily  raise  the  temperature  to  the  kindling  point  of 
the  phosphorus,  35-45°C.  The  element  burns  in  the  air, 
giving  off  dense  fumes  of  oxide  of  phosphorus.  In  oxygen 
it  burns  with  dazzling  brilliancy.  It  combines  directly 
with  many  other  elements  besides  oxygen,  such  as  sulphur 
and  the  halogens.  Phosphorus  is  exceedingly  poisonous, 
less  than  3^  of  one  gram  being  a  fatal  dose.  Continued 
exposure  to  its  vapor  causes  necrosis,  a  disease  in  which  the 
jawbones  and  teeth  are  particularly  liable  to  attack.  Work- 
ers in  match  factories  are  especially  subject  to  necrosis. 
A  mixture  of  phosphorus  and  flour  and  water  is  often  used 
as  a  poison  for  rats  and  other  vermin.  Phosphorus  is  a 
very  dangerous  chemical  not  only  on  account  of  its  poisonous 
character,  but  also  because  it  may  cause  painful  burns 
which  heal  very  slowly.  //  must  always  be  handled  with 
forceps. 


108  CHEMISTRY  OF  THE  FARM  AND  HOME 

Red  Phosphorus.  Yellow  phosphorus  under  certam  con- 
ditions may  gradually  change  from  the  yellow  material 
just  described  to  a  dark  red  powder.  Simple  standing 
of  the  yellow  variety  with  exposure  to  light  or  heating  to  a 
temperature  just  below  its  boiling  point  will  cause'  this 
change.  The  new  substance  differs  remarkably  from  the 
other.  Its  density  has  increased  to  2.1.  It  is  not  poison- 
ous, neither  is  it  soluble  in  carbon  disulphide,  nor  does  it 
take  fire  in  the  air  below  240°C.  If  distilled  and  quickly 
condensed,  the  red  form  changes  back  to  the  yellow  mod- 
ification again.  What  term  is  applied  to  such  physical 
modifications  of  a  single  element? 

Compounds  of  Phosphorus.  Phosphorus  forms  phos- 
phine,  PH3,  a  hydrogen  compound  which  is  analogous 
to  ammonia.  There  are  two  oxides  of  phosphorus,  the 
trioxide  and  the  pentoxide,  sometimes  called  phosphoric 
anhydride.  When  phosphorus  burns  in  an  insufficient 
supply  of  oxygen  or  air,  part  of  the  product  is  the  trioxide, 
P203-  When  there  is  an  excess  of  air  or  the  combustion 
takes  place  in  oxygen,  the  pentoxide  is  formed,  P2O5.  The 
latter  is  the  more  common  and  important  of  the  two.  It 
is  a  snow  white  light  powder  that  is  characterized  by  its  great 
attraction  for  water.  Since  it  does  not  react  with  most 
gases,  they  can  be  thoroughly  dried  by  passing  them  through 
a  proper  apparatus  containing  the  pentoxide.  These  two 
oxides  of  phosphorus  dissolve  in  water  and  give  the  acids 
of  phosphorus.  There  are  six  acids  formed  in  this  way, 
depending  upon  the  kind  of  oxide  and  the  amount  of  water 
concerned  in  the  reaction.  Phosphorous  acid  (H3PO3) 
is  not  a  common  compound  either  as  an  acid  or  its  salts. 
Phosphoric  acid  (H3PO4)  is  prepared  by  dissolving 
phosphorus  pentoxide  in  water  and  by  treating  tri-calcium 
phosphate  with  concentrated  sulphuric  acid.  It  is  the 
most  important  of  the  phosphorus  acids.  Many  of  its 
salts  occur  in  nature.     Pyrophosphoric  and  metaphosphoric 


SOME  OTHER  NON-METALS  109 

acids  are  the  names  of  the  other  acids.  They  are  not  of  very 
great  importance. 

Uses  of  Phosphorus.  The  chief  use  of  phosphorus  in 
the  elementary  form  is  in  the  manufacture  of  matches. 
Matches  may  be  divided  into  two  classes,  the  common  kind 
that  ignite  by  simple  friction,  and  the  safety  match  that 
requires  a  prepared  surface  for  this  ignition.  The  com- 
mon match  is  prepared  as  follows.  The  match  stick  is  dipped 
for  about  J/^  inch  into  some  inflammable  substance,  as 
melted  paraffin,  and  then  into  a  paste  of  phosphorus,  some 
oxidizing  substance,  as  potassium  chlorate,  and  a  binding 
material,  as  glue.  The  friction  of  rubbing  the  match  on 
any  surface  causes  enough  heat  to  ignite  the  phosphorus. 
The  combustion  is  aided  by  the  oxygen  liberated  from  the 
oxidizing  agent.  The  paraffin  is  then  ignited  and  finally 
the  wood.  The  process  is  really  one  of  setting  fire  to  a 
material  of  relatively  high  ignition  temperature  by  using 
a  series  of  substances  of  gradually  increasing  ignition  tem- 
perature. A  number  of  chemicals  may  be  used  as  substi- 
tutes for  those  mentioned  in  the  example  cited  above. 
Sulphur  replaces  the  paraffin  in  the  common  sulphur  match. 
Phosphorus  sulphide  may  take  the  place  of  the  phosphorus, 
manganese  dioxide  and  red  lead,  of  the  potassium  chlorate, 
and  dextrin,  of  the  glue. 

The  safety  match  cannot  be  readily  ignited  by  friction, 
except  on  a  prepared  surface.  The  match  tip  itself  contains 
an  oxidizing  substance,  as  potassium  chlorate  or  potassium 
dichromate,  an  easily  oxidized  material,  usually  antimony 
sulphide  or  sulphur,  some  powdered  glass  to  increase  the 
friction,  and  some  glue.  The  prepared  surface  is  usually 
on  the  side  of  the  match  box  and  consists  of  a  mixture  of 
red  phosphorus,  a  gritty  material,  as  emery  or  fine  sand,  and 
glue.  The  friction  of  the  match  against  the  surface  con- 
verts a  little  of  the  red  phosphorus  into  vapor  and  ignites 
the  match  tip.     The  combustion  is  maintained  by  the  re- 


110      CHEMISTRY  OF  THE  FARM  AND  HOME 

action    between    the    oxidizing   and    oxidized    substances. 
In  this  way  the  wood  is  finally  ignited. 

The  compound,  acid  calcium  phosphate,  H4Ca  (P04)2 
has  two  important  uses,  one  of  application  in  the  house- 
hold and  the  other  of  the  greatest  significance  to  agricul- 
ture. This  compound  is  used  in  the  preparation  of  the 
phosphate  baking  powders,  being  mixed  in  proper  propor- 
tion with  baking  soda  and  starch.  The  phosphate  is  acid 
in  reaction  and  together  with  the  soda  liberates  carbon 
dioxide.  The  greatest  use  of  acid  calcium  phosphate  is, 
however,  in  the  form  of  acid  phosphate  fertilizers.  Other 
compounds  of  phosphorus  are  important  for  the  same  pur- 
pose. As  already  stated,  phosphorus  is  a  constituent  of 
plants  and  is  necessarily  removed  from  the  soil  in  this  way. 
Since  the  supply  of  phosphorus  in  natural  soils  is  limited 
and  in  certain  cases  very  small,  it  can  readily  be  understood 
that  constant  cropping  of  the  land  will  diminish  the  amount 
of  this  material.  In  order  to  restore  this  fertility  and 
maintain  the  cropping  capacity  of  the  soil,  fertilizers  must 
be  added.  Bone  products,  as  bone  meal,  bone  ash,  etc., 
rock  phosphate  powder,  and  acid  phosphate  are  used  for 
this  purpose.  The  acid  phosphate  is  soluble  in  water,  the 
others  are  not,  but  may  become  gradually  soluble  under 
soil  conditions.  The  acid,  therefore,  has  the  great  advan- 
tage that  it  is  immediately  available  for  plant  use.  The 
other  forms  become  slowly  available  as  the  crops  require 
them.  It  should  be  kept  in  mind,  however,  that  acid  cal- 
cium phosphate,  also  called  super-phosphate,  quickly  reverts 
to  insoluble  phosphates  on  contact  with  the  soil.  Its  great 
advantage  comes  from  an  effective  fineness  of  distribution 
of  available  phosphorus  compounds  in  the  soil. 

CARBON 

Introduction.  Carbon  forms  only  about  one  five  hun- 
dredth of  the  weight  of  the  earth's  crust.  Yet  its  prop- 
erties are  such  that  it  is  one  of  the  most  important  chemical 


SOME  OTHER  NON-METALS  111 

elements.  It  is  the  characteristic  substance  of  plant  and 
animal  products ;  thus  it  is  essential  to  all  life  processes.  In 
the  mineral  kingdom  it  is  also  very  important.  Limestone, 
for  example,  contains  carbon.  Coal,  petroleum,  and  natural 
gas  contain  carbon.  It  is  generally  assumed  that  all  such 
carbonaceous  matters  are  derived  from  plant  and  animal 
origin.  Carbon  is  remarkable  for  the  very  large  number 
of  compounds  which  it  forms  with  other  elements,  espe- 
cially oxygen  and  hydrogen.  Compounds  of  carbon  are 
more  numerous   than  all   other  compounds   put  together. 

Distribution.  Carbon  occurs  in  nature  in  both  the 
elementary  and  compound  forms.  In  the  free  state  it 
occurs  in  the  three  allotropic  forms,  one  amorphous,  and 
two  crystalline,  namely  the  diamond  and  graphite.  All  these 
are  very  nearly  pure  carbon,  but  differ  in  their  properties 
from  one  another.  Amorphous  carbon  includes  a  number 
of  varieties  of  carbon  which  differ  merely  in  their  degree 
of  purity,  fineness  of  division,  and  mode  of  preparation. 

As  a  combined  substance  carbon  exists  in  an  enormous 
number  of  natural  compounds.  In  the  air  carbon  dioxide 
is  always  present  and  is  the  most  common  gaseous  com- 
pound of  the  element.  In  the  earth  certain  carbon  com- 
pounds exist  in  the  gaseous  form.  Natural  gas  is  a  mixture 
of  chemical  substances,  part  hydrogen  and  nitrogen,  but 
principally  compounds  of  hydrogen  and  carbon.  The  fire 
damp  of  mines,  methane,  is  such  a  compound.  Carbon 
dioxide  also  exists  as  a  gas  in  the  earth's  crust.  It  is  the 
deadly  choke  damp  of  mines  and  wells. 

Water  contains  carbon  dioxide  in  solution.  The  spark- 
ling character  and  the  effervescence  of  many  natural  spring 
or  mineral  waters  is  due  to  the  presence  of  carbon  dioxide. 
Moreover,  the  Hmestone  and  other  mineral  compounds  held 
in  solution  in  natural  waters  contain  carbon.  Petroleum 
oils,  deposits  of  which  exist  in  many  parts  of  the  world, 
rae  largely  composed  of  combined  carbon. 


112  CHEMISTRY  OF  THE  FARM  AND  HOME 

Many  solid  minerals  contain  carbon.  Examples  of  these 
are  the  different  kinds  of  coal  and  the  carbonates  of  metals 
which  constitute  great  strata  of  rocks  and  are  found  in  almost 
every  locality.  Calcium  carbonate  is  especially  important, 
as  it  is  found  in  enormous  deposits  of  limestone  and  marble. 
Other  important  carbonates  are  those  of  sodium,  magnes- 
ium, iron,  zinc,  copper  and  lead. 

All  vegetable  and  animal  substances  are  compounds  of 
carbon.  In  fact  they  are  generally  mixtures  of  many  different 
compounds.  The  number  of  carbon  compounds  constitut- 
ing the  great  variety  of  Hving  organisms  is  almost  without 
limit.  More  than  100,000  compounds  have  been  prepared 
artificially  which  contain  this  substance.  The  synthetic 
dyes  are  instances  of  this  type  of  compound. 

PREPARATION  AND  PHYSICAL  PROPERTIES  OF  CARBON 

The  Diamond.  Diamonds  are  found  in  considerable 
quantities  in  several  localities,  especially  in  South  Africa, 
the  East  Indies  and  Brazil.  When  found  they  are  usually 
covered  with  a  rough  coating  which  is  removed  in  the  pro- 
cess of  cutting.  Artificial  diamonds  may  be  prepared 
by  dissolving  carbon  in  molten  iron  and  causing  it  to  crys- 
talHze  under  great  pressure  and  at  a  high  temperature.  This 
is  done  by  plunging  the  molten  iron  into  cold  water.  The 
outer  layer  hardens  first,  then  the  inner  portions.  The 
carbon  is  forced  out  of  the  solution  under  pressure  and  forms 
small  crystals.  The  iron  is  dissolved  by  hydrochloric  acid 
and  the  diamonds  are  left  undissolved. 

The  diamond  is  a  crystalline  soHd  with  a  density  of  3.5. 
It  is  the  hardest  substance  known,  a  poor  conductor  of  heat 
and  electricity,  but  has  a  high  refractive  and  dispersive 
influence  upon  light.  It  varies  from  colorless  to  black. 
The  diamond  is  practically  pure  uncombined  carbon,  though 
it  may  contain  some  mineral  matter.  Few  chemical  agents 
have  any  action  upon  it;  but,  when  heated  in  oxygen  or 


SOME  OTHER  N0N-METAL8  113 

the  air,  it  blackens  and  burns,  forming  carbon  dioxide. 
Black  diamonds  as  well  as  broken  and  imperfect  stones 
which  are  valueless  as  gems  are  used  for  glass  cutting  and 
for  grinding  hard  substances. 

Graphite.  Graphite  is  found  in  large  quantities  in  Cey- 
lon, Siberia,  and  some  parts  of  the  United  States  and  Canada. 
The  purer  grades  are  rare,  however.  Artificial  graphite 
is  produced  in  somewhat  the  same  way  as  diamonds.  The 
molten  mass  of  iron  and  carbon  is  allowed  to  cool  by  itself. 
A  portion  of  the  carbon  separates  as  graphite  diffused 
throughout  the  iron.  In  large  quantities  for  commercial 
purposes,  graphite  is  manufactured  by  heating  carbon  in 
an  electric  furnace  with  3  per  cent  of  iron. 

Graphite  is  a  gray,  lead-like  solid,  which  is  very  shiny 
and  greasy  to  the  touch.  It  was  formerly  supposed  to 
be  a  pecuHar  form  of  lead.  Thus  it  has  long  been  called 
black  lead  and  plumbago.  Its  density  is  about  2.15.  The 
properties  of  graphite  vary,  depending  upon  its  source. 
It  is  more  easily  attacked  by  reagents  than  the  diamond. 
It  is  used  as  a  lubricant,  as  a  protective  covering  for  iron 
in  the  form  of  a  polish  or  paint,  and  in  the  manufacture  of 
lead  pencils  and  crucibles  for  industrial  purposes. 

Coal.  Coals  of  various  kinds  were  probably  formed 
from  the  accumulations  of  vegetable  matters  in  former 
years.  These  became  covered  with  earthy  material  and 
were  thus  protected  from  rapid  decay.  Under  various 
natural  agencies,  such  as  heat  and  pressure,  the  organic 
matter  was  slowly  changed  into  coal.  In  hard,  or  anthra- 
cite coal,  these  changes  have  gone  the  furthest  and  this 
variety  is  nearly  pure  carbon.  Soft,  or  bituminous,  coals 
contain  considerable  organic  matter  besides  carbon  and 
mineral  substances. 

Peat,  lignite,  soft  coal  and  anthracite  represent  in  a 
general  way  different  stages  in  the  decomposition  of  vege- 
table matter  in  the  absence  of  air.     Water  and  compounds 


114 


CHEMISTRY  OF  THE  FARM  AND  HOME 


of  carbon  and  hydrogen  are  given  off  in  the  process.  The 
following  table  shows  the  change  in  composition  and  the 
relations  of  the  substances  to  fresh  wood  on  the  one  hand  and 
charcoal   and   coke   on   the   other. 


Table  IV. —  A  Comparison  of  the  Composition  of  Fuels. 


Percentage  exclud- 
ing ash  and  moisture 

Percentage 
Ash 

Percentage 
Moisture 
(air  dry) 

Calorific 
value  per  gm. 

Carbon 

Hydrogen 

Wood 

45 
60 
70 
82 
94 
95 
96 

6 

6 

5 

5 

3 

1.7 

0.7 

1.5 

5-20 

3-30 

1-15 

1.5 

4 

3.4-11 

18-20 

20-30 

15 

4 

2 

6.5 

2 

2700 

Peat 

3500 

3000-6000 

Soft       

6600-8000 

Anthiacite 

Charcoal 

Coke 

7000-8000 
8080 
7700 

The  gradual  increase  in  the  percentage  of  carbon  and  the 
decrease  in  the  amount  of  hydrogen  is  apparent.  There  is 
also  an  increase  in  the  calorific  value  of  the  fuels  as  the 
scale  is  descended. 

Amorphous  Carbon.  There  are  many  varieties  of  amor- 
phous or  non-crystalline  carbon.  Pure  carbon  is  best 
prepared  by  charring  sugar.  The  other  elements  of  which 
sugar  is  composed,  hydrogen  and  oxygen,  are  driven  off  in 
the  form  of  water  and  pure  carbon  is  left  behind.  It  is  a 
soft,  black,  lustrous  powder. 

The  different  forms  of  amorphous  carbon  may  be  pre- 
pared in  more  or  less  pure  condition  by  heating  certain  car- 
bon compounds  without  access  of  air.  The  conditions 
are  such  that  but  little  oxidation  can  take  place. 

Lampblack  is  produced  when  tar,  resin,  petroleum, 
or  other  similar  substances  are  burned  with  an  insufficient 
supply  of  air  or  oxygen.  A  very  smoky  flame  is  produced. 
The  smoke  is  composed  of  minute  particles  of  lampblack 
which  may  be  collected  in  proper  receptacles.  Soot  is  also 
a  product  of  imperfect  combustion  of  oil  or  coal.  Both 
lampblack  and  soot  usually  contain  oily  impurities. 


SOME  OTHER  N0N-METAL8  115 

Charcoal  is  produced  by,  heating  wood  or  similar  vegetable 
matter  in  pits  or  retorts  in  such  a  way  that  only  a  very 
limited  combustion  can  follow.  The  older  method  was 
to  arrange  the  wood  in  a  pile,  cover  it  with  sods,  make  a 
few  openings  for  inlet  of  air,  set  the  pile  on  fire,  finally  close 
all  openings  and  allow  the  whole  to  cool.  At  first  the  car- 
bon and  hydrogen  of  a  part  of  the  wood  compounds  burn. 
Later,  however,  other  portions  of  the  wood  are  simply 
heated,  not  burned.  Their  hydrogen  and  oxygen  are 
liberated,  but  the  carbon  remains.  In  the  newer  process 
the  wood  is  heated  in  retorts  without  access  of  air.  The  pro- 
cess is  commonly  called  destructive  distillation.  The  wood  is 
decomposed,  the  hydrogen  and  oxygen  and  a  small  part  of 
the  carbon  are  expelled  as  gaseous  compounds,  and  the  lat- 
ter may  be  condensed  by  passing  them  through  cooled 
pipes.  The  charcoal  remains  in  the  retort.  The  older  pro- 
cess was  very  wasteful  since  no  effort  was  made  to  save  the 
compounds  liberated  as  gases.  These  are  recovered,  how- 
ever, in  the  newer  process,  and  include  wood  alcohol,  acetone, 
and  acetic  acid,  all  valuable  for  certain  commercial  uses. 
Charcoal  contains  the  mineral  compounds  present  in  the 
original    wood. 

Animal  Charcoal  is  prepared  by  a  process  similar  to  that 
by  which  wood  charcoal  is  produced.  Waste  animal  matters 
like  leather  clippings  are  heated  in  closed  retorts.  Bone 
charcoal  is  a  variety  of  animal  charcoal.  The  carbon  of 
the  organic  compounds  closely  associated  with  the  bony 
tissue  is  distributed  in  a  very  porous  condition  throughout 
the  bone  charcoal. 

Coke  is  produced  by  heating  soft  coal  so  that  only  a 
limited  combustion  may  result.  It  is  quite  important 
that  no  more  carbon  be  lost  by  the  method  than  is  abso- 
lutely necessary  from  the  nature  of  the  operation.  The 
bee-hive  oven  is  somewhat  like  the  older  method  for  the  pro- 
duction of  charcoal.     It  is  a  wasteful  process  since  no  effort 


116  CHEMISTRY  OF  THE  FARM  AND  HOME 

is  made  to  utilize  the  gases  given  off.  The  newer  coke 
ovens  are  designed  to  produce  coke,  but  at  the  same  time 
to  recover  the  gaseous  and  Uquid  materials  given  off  by  the 
treatment.  The  gases  are  used  for  illuminating  purposes. 
The  liquid  coal  tar  is  valuable.  This  is  a  complex 
mixture  which  may  be  refined  by  the  same  general  method 
used  in  refining  crude  petroleum.  Some  hydrocarbons, 
as  benzol  and  naphthalene,  and  carbolic  acid  and  aniline 
may  be  secured  from  the  tar.  These  serve  as  a  starting  point 
for  the  synthetic  dyes,  many  drugs,  and  other  chemicals. 
Ammonium  compounds  are  also  a  by-product  of  the  process 
and  they  are  valuable  for  all  the  uses  of  ammonia,  both 
household,  industrial,  and  agricultural.  Some  of  the  coke 
is  formed  as  a  dense  cake  on  the  sides  and  roof  of  the  retort. 
This  is  called  retort  or  gas  carbon  and  is  quite  pure  carbon. 

Lampblack,  vegetable  charcoal  and  animal  charcoal 
are  black  and  easily  powdered.  Coke  has  often  a  brilliant 
steel  color.  Gas  carbon  resembles  coke,  though  it  also  re- 
sembles graphite  in  some  respects.  These  are  all,  generally 
speaking,  poor  conductors  of  heat  and  electricity.  All 
forms  of  carbon  strongly  resist  attempts  to  melt  or  to  vapor- 
ize it,  though  the  electric  arc  probably  does  both. 

All  forms  of  carbon,  except  the  diamond,  exhibit  a 
remarkable  surface  adhesion  for  matters  in  solution  and  for 
gases.  For  this  reason  considerable  charcoal  is  used  as  a 
filtering  medium.  It  often  completely  decolorizes  colored 
liquids,  it  can  withdraw  certain  compounds  from  their 
solution,  and  it  can  absorb  large  quantities  of  water  vapor 
and  other  gases.  Another  characteristic  property  of  all 
forms  of  carbon  is  their  insolubility  in  liquid  solvents.  Prac- 
tically the  only  liquid  solvent  for  carbon  is  molten  iron. 
All  forms  are  odorless,  tasteless  solids,  insoluble  in  water 
and  characterized  by  their  stability  towards  heat. 

Chemical  Properties.  Carbon  is  one  of  the  most  re- 
markable of  the  elements  in  its  chemical  properties.     There 


SOME  OTHER  NON-METALS 


117 


is  at  present  a  greater  number  of  known  compounds  con- 
taining carbon  than  of  any  other  element.  The  chemical 
changes  taking  place  during  the  growth  of  plants  and  animals 
give  rise  to  an  enormous  number  of  carbon  compounds.  It 
is  possible  by  artificial  processes  in  the  laboratory  or  factory 
to  produce  a  large  number  of  carbon  compounds  which  are 
different  from  those  of  natural  origin.  Though  the  chem- 
ist may  make  numerous  substances  which  have  not  yet 
been  found  in  any  natural  source,  still  there  are  a  number 
of  natural  compounds  elaborated  by  plant  and  animal  life 
which  man  cannot  synthesize. 

Uncombined  carbon  is  very  inert  chemically  at  ordinary 
temperatures;   at   high  temperatures,   however,   it   has   a 


Figure  29. — Carbon  prepared  foi  industrial  uses. 


118 


CHEMISTRY  OF  THE  FARM  AND  HOME 


powerful  attraction  for  certain  elements,  especially  oxygen. 
The  different  forms  of  carbon  are  not  affected  by  ordinary 
reagents,  but  at  higher  temperatures  carbon  combines  with 
many  elements  forming  carbides.  Only  two  oxides  of 
carbon  are  known,  but  there  are  more  than  a  hundred  com- 
pounds of  carbon  and  hydrogen. 

Uses  of  Carbon.  The  principal  use  of  amorphous  car- 
bon is  as  fuel  to  furnish  heat  and  power  for  all  the  demands 
of  civilization.  Enormous  amounts  of  carbon  in  the  form 
of  charcoal  and  coke  are  used  in  extracting  metals  from 
their  ores,  especially  iron.  Retort  carbon  and  coke  are  used 
for  making  electric  light  carbons  and  battery  plates  (Fig- 
ure 29).     Lampblack  is  used  for  printers'  ink,  indelible  inks 

and  black  varnishes. 
Boneblack  and  char- 
coal are  used  for  fil- 
tering agents,  the 
former  especially  in 
sugar  refineries. 

Compounds  of 
Carbon  with  Oxy- 
gen. Carbon  monox- 
ide, CO.  This  com- 
pound is  a  light,  col- 
orless, almost  odor- 
less gas  which  is  very 
difficult  to  liquefy. 
It  is  very  poisonous, 
combining,  when  in- 
haled, with  the  red 
coloring  matt e r  of 
the  blood  and  preventing  the  proper  absorption  of  oxygen.  It 
burns  with  a  pale  blue  flame,  forming  the  other  oxide  of  car- 
bon, carbon  dioxide.  Carbon  monoxide  is  very  active  chem- 
ically, combining  directly  with  many  substances. 


Figure  30. — A  producer  gas  plant. 


SOME  OTHER  N0N-METAL8 


119 


Carbon  monoxide  may  be  prepared  in  the  laboratory  by 
decomposing  oxalic  acid  with  strong  sulphuric  acid.  It  is 
prepared  cornmercially  on  a  large  scale  by  passing  steam 
over  red-hot  carbon.     This  process  gives  a  mixture  of  hy- 

C  +  H20->CO  +  H2 
drogen  and  carbon  monoxide,  the  so-called  water  gas,  which 
is  extensively  used  for  fuel  purposes.     Figure  30  shows  a 

diagrammatic  sketch  of  a  pro- 
ducer gas  plant,  which  also 
gives  carbon  monoxide  mixed 
with  nitrogen.      Air  is  passed 
through  heated   carbon,    and 
the  final  products   are  those 
stated.     Steam  may  be  used 
in  manufacturing  producer  gas 
as  well  as  water  gas.     In  both 
cases  the  carbon  is  partially 
oxidized  with  steam.    Carbon 
monoxide    is    the    gas   which 
burns  with  its   characteristic 
flame  on  the  surface  of  a  coal 
fire,  when  the  stove,  having  a  good  fire  in  the  lower  parts, 
has  a  relatively  large  supply  of  coal  higher  up.     Figure  31. 
The  carbon  dioxide  formed  at  first  is  reduced  to  carbon 
CO2  +  C  ->  2  CO 
2C0  +O2  -^  2CO2 
monoxide  by  coming  in  contact  with  the  highly  heated  car- 
bon.    It  combines  with  more  oxygen  on  the  surface  and 
burns  to  form  carbon  dioxide.     It  is  the  presence  of  carbon 
monoxide  in  coal  gas  that  is  responsible  for  the  death  of 
many  human  beings,  since  it  escapes  into  the  house  when 
there  is  insufficient  draught  in  the  stove. 

Carbon  dioxide,  CO2.  This  compound  is  produced  in  a 
variety  of  ways.  (1)  Whenever  carbon  burns  or  oxidizes 
with  suflftcient  oxygen,  carbon  dioxide  is  formed.    This  is 


Figure    31. — The  production  of  car- 
bon monoxide  in  a  coal  fire. 


120 


CHEMISTRY  OF  THE  FARM  AND  HOME 


true  of  both  free  and  combined  carbon.  The  burning  of 
fuels,  the  decay  of  plant  and  animal  matter  and  the  breath- 
ing of  animals  give  rise  to  carbon  dioxide.  (2)  When  cer- 
tain carbonates  are  heated,  carbon  dioxide  is  evolved.  In 
the  production  of  quick-lime  much  carbon  dioxide  is  given 
off  from  the  highly  heated  limestone.  (3)  The  reaction 
between  carbonates  and  acids  gives  carbon  dioxide. 
CaCOs  +  2  HCl  -^  CO2  +  CaClg  +  H2O 

At  ordinary 
temperatures  car- 
bon dioxide  is  a 
gas,  which  is  col- 
orless and  practic- 
ally odorless.  By 
lowering  the  tem- 
perature either 
with  or  without  a 
simultaneous  in- 
crease of  pressure, 
it  may  be  reduced 
to  a  colorless  liq- 
uid. When  this  is 
allowed  to  escape 
into  the  air,  part  of 
it  instantly  evap- 
orates and  absorbs 
so  much  heat  that 
another  portion  is 
soUdified  to  a  snow- 
like material. 

Carbon  dioxide  is  about  one  and  one  half  times  as  heavy 
as  the  air,  one  liter  weighing  1.9641  grams.  The  gas  is 
moderately  soluble  in  water  at  ordinary  temperature  and 
pressure  and  imparts  a  somewhat  biting,  pungent  taste  to 
it.     Such  solutions  are  called  carbonic  acid  though  this  com- 


Flgure  32. — An  automatic  fire  extinguisher. 


SOME  OTHER  NON-METALS  121 

pound  is  more  or  less  of  a  hypothetical  nature.  It  is  very 
unstable  and  cannot  be  isolated.  The  relatively  slight 
solubility  of  carbon  dioxide  in  water  proves  that  very  little 
of  the  acid  is  formed.  If,  however,  bases  are  present  in 
the  water,  salts  of  carbonic  acid  are  produced  which  are  quite 
stable.  The  effect  of  carbon  dioxide  dissolved  in  rain 
water  and  soil  water  is  very  great  upon  the  earth's  surface. 
Limestone,  especially,  is  very  soluble  in  such  water. 

Carbon  dioxide  will  not  combine  with  more  oxygen  and, 
therefore,  will  not  burn.  Living  animals  plunged  into  an 
atmosphere  of  the  gas  die  by  suffocation  or  drowning.  In- 
stances of  deaths  from  this  gas,  choke  damp,  in  mines,  wells 
and  even  silos  are  very  common.  It  is  always  safer  to  lower 
a  lighted  candle  in  silos  or  wells  before  descending  into 
them.  If  the  candle  burns,  it  is  safe;  if  the  candle  goes  out, 
it  indicates  that  there  is  no  oxygen  there  to  support  combus- 
tion or  breathing.  Burning  substances  are  generally  ex- 
tinguished in  carbon  dioxide.  Use  is  made  of  this  fact  in 
the  preparation  of  automatic  fire  extinguishers.  Figure  32. 
The  main  portion  of  the  apparatus  is  a  tank  for  a  water 
solution  of  sodium  bicarbonate.  At  the  top  is  a  support 
for  a  bottle  of  sulphuric  acid.  When  the  apparatus  is  need- 
AT.-.  OS  PH ERE  ed,  it  is  inverted 

and  the  acid  and 
BACTERIAL. i-iF-EiX  \  ^^^^ PL.ANT uiFE.   carbouatc  inter- 

mingle, producing 
carbon  dioxide. 
The  water  carry- 
ing the  gas  is  ex- 
THEisoiL-  V  ^ANir-iAu  i-»FE.  pcUcd  undcr presS" 

ure  and   may  be 

Figure  33. — The  cycle  of  carbon.  t        ,     i  .i 

directed  upon  the 
fire.  The  carbon  dioxide  being  heavier  than  air  settles 
around  the  fire,  crowding  away  the  oxygen  and  extinguish- 
ing the  flame. 


122  CHEMISTRY  OF  THE  FARM  AND  HOME 

Cycle  of  Carbon.  The  circulation  of  carbon  is  shown  in 
the  diagrammatic  sketch,  Figure  33.  The  carbon  of  plant 
and  animal  life  comes  from  the  atmosphere  and  may  be  re- 
turned to  the  atmosphere  by  them  directly;  or  the  element 
may  be  returned  to  the  soil  and  then  acted  upon  by  bacterial 
life  and  again  evolved  into  the  air  in  the  form  of  carbon 
dioxide.  In  other  words,  the  atmosphere  is  the  great 
storehouse  of  this  element,  which  is  so  essential  to  the  life 
of  plants  and  animals. 

SOME  SIMPLE  ORGANIC  COMPOUNDS 

Introduction.  Chemistry  may  be  divided  into  two  great 
divisions,  organic  and  inorganic.  It  was  originally  thought 
that  those  substances  which  constitute  minerals  and  rocks 
were  to  be  regarded  as  inorganic  in  character;  that  those 
substances  which  are  produced  by  the  life  force  of  different 
organisms,  whether  plant  or  animal,  were  to  be  called  or- 
ganic. When,  however,  it  was  found  that  certain  compounds 
characteristic  of  life  processes  can  be  prepared  in  the  lab- 
oratory from  inorganic  materials,  the  line  of  division  between 
these  two  classes  could  no  longer  be  held.  Almost  all  the 
compounds  found  in  living  organisms  contain  carbon.  There 
are  over  100,000  compounds,  which  do  not  occur  in  plants 
and  animals,  but  have  been  prepared  artificially,  which  con- 
tain carbon.  The  term  organic  chemistry  at  the  present 
time  includes  both  these  artificial  and  natural  substances. 
Organic  chemistry  has  become  the  chemistry  of  the  com- 
pounds of  carbon.  Inorganic  chemistry  treats  of  all  other 
substances.  Usually  the  simpler  compounds  of  carbon, 
as  the  oxides  and  carbonates,  are  included  in  inorganic 
chemistry. 

The  carbon  compounds  excel  in  number  those  of  all  the 
other  elements  together,  yet  each  compound  is  composed 
of  relatively  few  elements.  Many  compounds  contain  only 
carbon  and  hydrogen  and  many  more  contain  carbon,  hydro- 


SOME  OTHER  NON-METALS  123 

gen  and  oxygen.  A  number  of  important  organic  substances 
contain  carbon,  hydrogen  and  nitrogen  while  others  have 
oxygen  in  addition.  Phosphorus,  sulphur  and  the  halo- 
gens are  also  present  in  many  organic  compounds. 

The  great  number  of  carbon  compounds  can  be  grouped 
into  classes  of  similar  compounds.  It  is  possible  to  study 
the  properties  of  each  class  as  a  whole.  Knowing  the  gen- 
eral properties  one  may  predict  the  characteristics  of  any 
member  of  that  class.  Some  of  the  most  important  of  these 
classes  are  hydrocarbons,  alcohols,  aldehydes,  acids,  ethereal 
salts,  ethers,  the  organic  bases  and  the  carbohydrates. 

The  Hydrocarbons,  compounds  of  carbon  with  hydro- 
gen. Such  compounds  often  occur  in  nature  in  natural 
gas  and  petroleum.  Others  are  found  in  living  plants  and 
others  are  produced  by  the  decay  of  organic  matter  in  the 
absence  of  air.  They  may  be  made  artificially  by  a  variety 
of  methods.  The  heating  of  organic  matter  without  access 
of  air  is  a  general  process,  though  there  is  a  number  of 
special  methods  for  each  particular  compound. 

Methane,  or  marsh  gas,  CH4,  is  a  very  common  example 
of  a  hydrocarbon.  It  is  found  in  marshes,  being  formed 
by  the  decay  of  vegetable  matter  under  water.  It  consti- 
tutes about  90%  of  natural  gas  and  also  collects  in  mines, 
coming  from  the  pockets  in  coal  beds.  In  the  latter  case 
its  mixture  with  air  is  often  called  fire  damp  on  account 
of  its  inflammable  and  explosive  nature.  It  is  one  of  the 
chief  constituents  of  coal  gas.  Methane  is  a  colorless  and 
odorless  gas  and  burns  with  a  pale  blue  flame.  Its  density 
is  0.55,  it  is  almost  insoluble  in  water  and  is  difficult  to  liquefy. 

In  methane  each  of  the  four  valencies  of  carbon  is  sat- 
isfied with  a  hydrogen  atom.  The  structure  of  this  com- 
pound may  be  shown  graphically  somewhat  as  follows: 
H-c-H.  Other  carbon  compounds  can  be  formed  from  this 
one  by  replacing  any  one  or  more  of  the  hydrogens  by  other 


124 


CHEMISTRY  OF  THE  FARM  AND  HOME 


suitable   elements   or   groups   of   elements.     For   example, 
H-c-OH,   in  which    one    H    has    been    replaced   by    an    OH 


H 


H 

H-G-Cl 

H 


group.      Other    possible    derivatives    of    CH4    are 

TT     TT 

H-C-C-H,  etc. 
H  H 

Acetylene,  C2H2,  is  the  gas  commonly  prepared  by  the 
action  of  water  upon  calcium  carbide. 

CaC2  +  2  H2O  -^  C2H2  +  Ca(0H)2. 
It  is  a  colorless  gas  at  ordinary  temperatures  and  burns 
in  the  air  with  a  smoky  flame.  It  is  used  generally 
with  a  special  burner  which  gives  the  right  admixture 
of  oxygen  and  produces  an  intensely  luminous  flame. 
Its  use  for  lighting  bicycle  and  automobile  lamps  and  farm 
houses  is  very  well  known. 

Benzene,  CeHe,  is  separated  from  coal 
tar.  It  is  a  colorless  hquid  which  is  very 
volatile.  It  is  the  starting  point  for  the 
many  coal  tar  or  synthetic  dye-stuffs. 

Petroleum  and  its  Products.  The  chief 
oil  producing  regions  and  the  best  known 
are  those  in  Pennsylvania,  Ohio,  Kansas, 
California,  and  Texas  in  the  United  States, 
and  those  in  Mexico  and  Russia.  There 
are  other  valuable  sources  of  petroleum, 
however,  which  are  being  investigated  at 
the  present  time  in  Japan,  India,  and  Asia 
Minor. 

Petroleum  is  a  thick  oily  liquid.  It 
consists  essentially  of  a  mixture  of  hydro- 
carbons with  larger  or  smaller  amounts  of 
nitrogen  and  sulphur  compounds.  It  is 
principally  liquid  hydrocarbons  in  which 
are  dissolved  both  gaseous  and  solid  hydrocarbons.  Some 
crude  petroleum  is  used  as  a  fuel  and  to  enrich  water  gas, 


Figure  34. — A  portable 
gasoline  lamp. 


SOME  OTHER  NON-METALS 


125 


but  most  of  it  is  refined.  It  is  treated  successively  with 
sulphuric  acid,  caustic  soda  and  water.  It  is  then  distilled 
and  the  distillates  which  pass  over  between  certain  degrees 
of  temperature  are  collected  by  themselves.  Some  well 
known  liquids  collected  in  this  way  are  gasoline,  benzene, 
petroleum  ether  and  kerosene  or  coal  oil.      These  are  all 

used  as  fuels  and  solvents.  The 
higher  boiling  products  are 
converted  into  mineral  lubricat- 
ing oils,  vaseline  and  paraffin. 
None  of  these  products  is  a 
definite  chemical  compound, 
but  each  consists  of  a  mixture 
of  hydrocarbons,  the  boiling 
^  points  of  which  lie  within  cer- 
i  tain  limits.  After  the  distilla- 
tion process,  coke  remains  in 
the  retort.  Over  200  commer- 
cial products  are  now  made 
from  petroleum.  One  of  the 
principal  applications  of  petro- 
leum products  has  been  that  of 
using  them  for  producing  light, 
heat  and  power.  Kerosene  was 
formerly  the  material  most  com- 
monly utilized  for  this  purpose; 
but,  within  the  last  few  years, 
gasoline   has  become  of   equal 

Figure  35.  —  Diagrammatic  construe-    importance    and     thoSC     oils     of 
tion  of  a  gasolme  lamp.  ^ 

higher  boiling  points  are  broken 
into  gases  which  can  be  used  in  the  same  way.  As  an 
illustration  of  the  utility  of  gasoHne,  Figures  34  and  35  show 
a  portable  lamp  and  its  diagrammatic  construction  which 
is  largely  used  for  lighting  both  city  and  country  dwellings. 
In  this  type  of  lamp  the  gasoline  is  pumped  over  by  air 


126 


CHEMISTRY  OF  THE  FARM  AND   HOME 


pressure,  vaporized,  mixed  with  air  and  lighted  at  the 
outlet  of  the  lamp.  In  the  cross  section  of  the  lamp  is 
shown  (A)  the  asbestos  filter  tube  through  which  the  gasoline 
liquid  passes,  (B)  the  valve  controlling  the  supply  of  liquid, 
(C)  the  tube  that  is  heated  to  vaporize  the  gasoline,  (D)  the 
air  inlet  and  mixing  chamber,  and  (E)  the  burner.  Figure  36 
shows  a  cross  section  of  a  large  plant  for  supplying  gasoline 


M"W 

-  1  r,A\     ff  Ij. 

In 

E     \              c 

••■0 

:ga^- 

^E\j 

« 

1 

^^^T^ 

"7^^  *      ^ 

Figure  36. — A  large  gasoline  gas  plant. 

gas  for  a  dwelling  or  laboratory.  The  gasoline  is  vaporized 
by  a  current  of  air  and  piped  to  wherever  it  may  be  required. 

In  other  cases  the  heavier  petroleum  oils  are  subjected 
to  a  heat  treatment  which  gives  a  mixture  of  gases.  These 
are  liquefied  under  pressure  in  gas  holders  similar  to  those 
which  are  used  for  the  transportation  of  oxygen  and  hydro- 
gen. Upon  releasing  the  pressure  the  liquid  vaporizes  and 
the  gas  produced  may  be  burned.  This  is  the  character  of 
the  Pintsch  and  Blau  gases  which  are  used  for  lighting  rail- 
road coaches  and  country  residences. 

The  Alcohols.  The  alcohols  form  a  large  and  important 
class  of  organic  substances.  The  most  common  are  methyl, 
or  wood  alcohol,  and  ethyl,  or  grain  alcohol. 

Methyl  Alcohol,  CH3OH,  is  obtained  entirely  from  the 
dry  distillation  of  wood.  It  is  a  colorless  liquid,  having 
a  density  of  0.79  and  boiling  at  66°C.     It  burns  with  a 


SOME  OTHER  NON-METALS  127 

colorless,  hot  flame.  As  it  is  a  good  solvent  for  organic 
substances,  it  finds  many  uses,  especially  in  the  manufac- 
ture of  varnishes,  but  is  very  poisonous. 

Ethyl  Alcohol,  C2H5OH,  is  formed  by  the  fermentation  of 
sugar  (glucose).  Like  methyl  alcohol  it  is  a  colorless  liquid 
and  burns  with  a  colorless  hot  flame  which  does  not  deposit 
carbon  as  oil  flames  do.  It  boils  at  78°C.  and  has  a  density 
of  0.78.  It  has  a  number  of  important  uses,  such  as  a 
solvent  for  fats,  the  preparation  of  essences,  extracts,  per- 
fumes and  medicines,  the  preservation  of  anatomical  speci- 
mens, and  the  manufacture  of  thermometers  which  are 
exposed  to  very  low  temperatures.  Mercury  freezes  at 
—  39.5°C.,  while  ethyl  alcohol  does  not  solidify  until  it 
reaches  -112.3°C. 

Ethyl  alcohol  is  used  not  only  for  the  above  mentioned 
purposes,  but  also  for  the  manufacture  of  spirituous  liquors. 
The  starch  of  potatoes,  grains,  rice,  etc.,  is  changed  by 
means  of  certain  ferments  called  diastatic  enzymes,  into 
glucose  and  maltose.  Malt,  produced  from  germinating  bar- 
ley, is  used  to  bring  this  reaction  about.  The  glucose  or 
maltose  is  fermented  into  alcohol  by  the  addition  of  yeast. 
Carbon  dioxide,  glycerine,  and  other  alcohols  are  also  formed 
in  the  process.  The  ethyl  alcohol  is  distilled  from  the  mix- 
ture of  other  alcohols  called  fusel  oil.  The  last  traces  of 
water  are  removed  from  the  commercial  alcohol  by  distil- 
ling it  with  lime. 

In  small  quantities  alcohol  causes  intoxication;  in  large 
quantities  it  acts  as  a  poison.  The  intoxicating  properties 
of  such  liquors  as  beer,  wine,  and  whiskey  are  due  to  the 
alcohol  present.  Beer  contains  from  2  to  5%  of  alcohol, 
wine  from  5  to  20%,  and  whiskey  about  50%.  The  ordi- 
nary alcohol  of  the  druggist  contains  about  94%  alcohol 
and  6%  water.     100%  alcohol  is  called  absolute  alcohol. 

The  cost  of  manufacture  of  94%  alcohol  is  about  35 
cents  a  gallon.     There  is  a  tax  of  $2.00  a  gallon,  however, 


128  CHEMISTRY  OF  THE  FARM  AND  HOME 

imposed  by  the  government,  which  makes  it  impossible 
from  an  economical  point  of  view  to  use  this  in  manufac- 
turing processes.  In  1906  Congress  passed  an  act  by  which 
the  tax  is  removed  from  alcohol,  provided  it  is  denatured. 
This  means  that  the  alcohol  is  mixed  with  some  substance 
that  prevents  its  use  as  a  beverage,  but  will  not  interfere 
with  its  use  for  manufacturing  processes.  Wood  alcohol 
and  pyridine  are  some  substances  that  are  added  to  dena- 
ture alcohol.  The  possible  utilization  of  alcohol  as  fuel  to 
take  the  place  of  kerosene  and  gasoline,  when  the  natural 
supply  of  the  latter  is  exhausted,  adds  another  point  of  in- 
terest and  extreme  importance  to  this  compound. 

Glycerine,  C3H5(OH)3.  This  compound  is  an  alcohol 
with  three  hydroxyl  groups.  It  is  a  sweet,  colorless, 
oily  liquid,  which  is  prepared  from  fats  in  the  process  of 
making  soap.  It  is  used  in  the  manufacture  of  nitroglyc- 
erine and  dynamite,  soaps,  pharmaceutical  preparations,  inks, 
as  a  food  preservative  and  a  lubricant. 

Aldehydes.  Formaldehyde  is  made  by  oxidizing  methyl 
alcohol,  drawing  air  through  warm  alcohol,  and  passing  the 
warm  mixture  of  vapors  over  heated  copper.  It  is  a  color- 
less irritating  gas  and  very  soluble  in  water.  The  name 
formalin  is  applied  to  the  40%  water  solution  of  formalde- 
hyde. This  solution  is  used  as  a  disinfectant  and  preserva- 
tive and  in  agriculture  for  treating  seed  grains  and  potatoes 
to  prevent  fungous  diseases  from  attacking  them. 

Organic  Acids.  These  compounds  are  the  direct  pro- 
ducts of  the  oxidation  of  aldehydes. 

Acetic  acid,  CH3COOH,  is  formed  by  the  dry  distillation 
of  wood.  The  crude  product  is  called  pyroligneous  acid. 
Pure  acetic  acid  is  called  glacial  acetic  acid,  since  it  solidifies 
at  17°C.  and  is  thereby  separated  from  any  water  which 
may  be  present.  Vinegar  is  dilute,  impure  acetic  acid 
which  is  formed  by  the  fermentation  of  alcohol.  This  is 
effected  by  the  agency  of  a  small  organism  commonly  called 


SOME   OTHER   NON-METALS  129 

mother  of  vinegar.  The  various  kinds  of  vinegar,  are  made 
by  this  process.  In  the  manufacture  of  cider  vinegar,  the 
sugar  present  in  the  cider  first  undergoes  alcoholic  fermenta- 
tion. The  alcohol  then  undergoes  acetic  fermentation. 
The  amount  of  acetic  acid  in  vinegars  varies  from  three  to 
six  per  cent.  Acetic  acid  is  a  colorless  liquid  and  has  a 
strong  pungent  odor. 

Butyric  acid  is  present  in  butter  and  is  set  free  when  the 
butter  becomes  rancid.  The  ordinary  flavor  of  butter  is 
partly  due  to  the  presence  of  derivatives  from  butyric  acid. 

Oxalic  acid  is  found  in  certain  plants,  especially  the 
sorrels. 

Lactic  acid  is  produced  by  the  fermentation  of  milk  sugar 
and  is,  therefore,  found  in  sour  milk.  It  is  present  also  in 
pickles,  in  silage  and  in  the  gastric  juice. 

Tartaric  acid  occurs  either  in  the  free  form  or  as  salts 
in  many  fruits.  Potassium  acid  tartrate,  cream  of  tartar, 
is  obtained  from  the  walls  of  wine  casks  as  a  dark  solid 
called  tartar  or  argol.  The  so-called  cream  of  tartar  baking 
powders  consist  of  a  mixture  of  cream  of  tartar,  baking 
soda,  and  starch.  When  water  is  added  to  this  mixture, 
the  cream  of  tartar  reacts  with  the  soda,  liberating  car- 
bon dioxide,  which  escapes  through  the  dough  and  makes 
it  hght  and  porous. 

Malic  acid  occurs  in  fruits.  Citric  acid  occurs  in  lemons, 
oranges  and  other  acid  fruits. 

Esters  are  salts  of  alcohols  and  acids.  There  are  many 
of  them  present  in  fruits  and  flowers,  causing  their  char- 
acteristic odor  and  taste.  Some  of  these  compounds  which 
are  the  natural  flavors  of  drinks,  extracts  and  perfumes  can 
be  prepared  artificially  and  are  often  used  instead  of  the 
natural  flavors. 

Fats  and  oils.  The  most  important  esters  are  the  natural 
fats  and  oils  which  consist  essentially  of  compounds  of  gly- 
cerine with  stearic,  oleic  and  palmitic  acids.      These  esters 


130  CHEMISTRY  OF  THE  FARM  AND  HOME 

are  called  stearin,  olein,  and  palmitin.  Olein  is  a  liquid  fat; 
the  other  two  are  solids.  The  relative  amount  of  olein  con- 
sequently determines  the  fluidity  of  fats.  Tallow  and  beef 
suet  are  largely  stearin.  Palm  oil  is  largely  palmitin. 
Lard  and  olive  oil  contain  much  olein.  Butter  is  a  mixture 
of  several  fats. 

Soap  is  prepared  by  treating  fats  with  alkalies  until  the 
fats  have  been  broken  down  into  glycerine  and  alkali  salts 
of  the  acids  mentioned  above.  The  process  is  generally 
referred  to  as  saponification.  The  soap  is  soluble,  but  may 
be  precipitated  out  of  the  mixture  by  adding  much  salt, 
Hterally  salting  it  out.  The  glycerine  may  be  separated 
by  mechanically  working  it  out.  The  soap  is  washed  to 
free  it  from  alkali,  perfumed,  colored  and  perhaps  filled 
with  borax  or  other  material,  depending  upon  its  use  and 
character.  Hard  soaps  consist  of  the  sodium  salts,  and 
soft  soaps  of  the  potassium  salts  of  the  fatty  acids.  Palm 
oil,  cocoanut  oil,  butter  and  lard  produce  white  soaps. 
Castile  soap  is  made  from  olive  oil.  The  cheaper  soaps  or 
the  yellow  varieties  are  made  by  mixing  fats  with  rosin, 
cottonseed  oil,  bone  grease,  etc.  When  soaps  are  used  with 
water  containing  calcium  or  magnesium  salts  in  solution, 
these  metals  combine  with  the  acids  of  the  soap  and  form  in- 
soluble compounds  which  are  precipitated.  In  this  way 
much  soap  is  consumed  before  it  gives  rise  to  its  character- 
istic lather  or  suds. 

Ethers.  Ordinary  ether,  ethyl  ether  or  sulphuric  ether, 
(C2H5)20,  is  a  colorless,  volatile  liquid  with  a  sweet  odor. 
It  boils  at  a  very  low  temperature,  35°C.,  and  is  very  in- 
flammable. It  is  used  as  a  solvent  for  fats  and  other  com- 
pounds and  as  an  anaesthetic  in  surgery.  Ether  is  pre- 
pared from  ethyl  alcohol  by  the  action  of  sulphuric  acid. 

Carbohydrates  are  compounds  of  carbon  with  hydrogen 
and  oxygen,  the  latter  two  being  in  the  same  proportion  in 
which  they  occur  in  water.     The  most  important  substances 


SOME  OTHER  NON-METALS  131 

of  this  class  of  compounds  are  sugars,  starches  and  cellu- 
lose. Cane  sugar,  or  sucrose,  C12H22O11,  is  the  most 
common  sugar.  Maltose,  malt  sugar,  and  lactose,  milk 
sugar,  have  the  same  percentage  composition  of  hydrogen, 
oxygen  and  carbon  as  sucrose,  but  the  arrangement  of 
these  elements  is  different.  These  three  sugars,  therefore, 
have  slightly  different  properties.  Cane  sugar  melts  at 
160°C.  and  at  200°  it  forms  a  brown  substance  called  caramel 
which  is  used  for  coloring  foods  and  beverages.  Milk 
sugar  is  not  as  sweet  as  cane  sugar.  In  fact,  its  sweetness 
is  hardly  perceptible.  It  is  used  in  prepared  foods  and 
homeopathic  pellets. 

Cane  sugar  is  prepared  from  either  the  sugar  cane  or  the 
sugar  beet.  The  plant  material  is  crushed  or  pulped  and 
the  juice  extracted.  The  juice  is  clarified  by  means  of 
lime,  then  evaporated  in  vacuum  pans  to  prevent  the  char- 
ring and  decomposition  of  the  sugar.  The  sugar  crystals 
are  separated  from  the  molasses  by  centrifuging.  Raw  or 
brown  sugar  is  thus  obtained.  This  is  refined  by  dissolving 
in  water  and  filtering  through  animal  charcoal.  The  juice 
may  again  be  concentrated  and  then  crystallized.  Maple 
sugar  is  made  by  evaporating  the  sap  obtained  from  the 
hard  maple  tree.  Its  sweetness  is  due  to  the  presence  of 
cane  sugar,  though  other  products  present  in  the  maple 
syrup  impart  its  characteristic  flavor. 

Glucose,  or  dextrose,  or  grape  sugar,  C6H12O6,  is  a 
white  crystalline  soUd  which  is  less  sweet  than  cane  sugar. 
It  melts  at  150°C.  It  is  found  in  many  fruits,  especially 
grapes,  from  which  it  obtains  its  name.  It  also  occurs  in 
the  seeds,  the  roots,  leaves  and  blossoms  of  plants.  It  is 
formed  by  the  breaking  down  of  sucrose  and  starch  by 
enzyme  action.  Glucose  may  be  produced  artifically  by  treat- 
ing starch  with  acids.  Since  it  is  cheaper  than  cane  sugar, 
it  is  manufactured  extensively  and  is  used  in  making  jellies, 
candy  and  syrups.     Glucose  is  commonly  called  corn  syrup. 


132      CHEMISTRY  OF  THE  FARM  AND  HOME 

Fructose,  or  levulose,  or  fruit  sugar,  C6H12O6,  has  the 
same  percentage  composition  as  glucose,  but  the  atoms 
composing  the  molecule  are  differently  arranged.  It  occurs 
in  fruits  and  honey. 

Starch  (C6Hio05)x  is  found  in  grains,  potatoes  and 
fruits.  It  can  be  mechanically  separated  by  means  of  water 
from  its  mixture  with  other  compounds  in  corn  and  pota- 
toes. In  the  United  States  it  is  obtained  chiefly  from  corn, 
nearly  80%  of  which  is  starch.  In  Europe  it  is  secured 
principally  from  the  potato.  Starch  consists  of  small 
grains.  The  appearance  varies  depending  upon  the  source 
of  the  starch.  Chemically,  however,  all  kinds  of  starch 
are  the  same.  Hot  water  causes  the  grains  to  swell  and 
burst.  The  starch  paste  thus  formed,  when  suspended  in 
water,  gives  starch  solution,  though  the  starch  does  not 
form  a  true  solution.  Starch  is  used  in  foods,  in  making 
cloth,  paper  and  glucose,  and  for  starching  clothes. 

Dextrin  is  formed  from  starch  by  the  action  of  heat  or 
dilute  acids.  Impure  dextrin  is  a  sticky  substance  used  for 
mucilage. 

Cellulose,  (C6Hio05)x,  is  the  frame  work  of  the  plant,  as 
it  forms  the  walls  of  the  plant  cells.  Cotton,  linen,  and 
paper  are  almost  entirely  cellulose.  The  finer  grades  of 
paper  are  made  from  linen  and  cotton  rags,  the  cheaper 
grades  from  straw  and  wood.  Swedish  filter  paper  is  a 
purified  form  of  cellulose.  Cellulose  is  an  amorphous  white 
substance  insoluble  in  most  solvents.  When  treated  with 
concentrated  sulphuric  acid  it  is  decomposed  into  glucose. 
Nitric  acid  gives  nitro-cellulose,  sometimes  called  pyroxylin, 
or  gun  cotton,  used  as  an  explosive.  When  exploded  it 
yields  only  colorless  gases;  hence  it  is  used  especially  in  the 
manufacture  of  smokeless  gunpowder.  Collodion  is  nitro- 
cellulose dissolved  in  alcohol  and  ether.  When  the  solvent 
evaporates  it  leaves  a  thin  film  of  tough  transparent  mate- 
rial.    This  can  be  used  to  make  photographic  films  and  to 


SOME  OTHER  NON-METALS  133 

protect  wounds.     Celluloid  is  a  mixture  of  gun  cotton  and 
camphor. 

Alkaloids  are  nitrogenous  substances  occuring  in  many 
plants  and  trees  and  often  used  in  medicine  on  account  of 
their  physiological  effect.  Chemically  they  resemble  am- 
monia, their  aqueous  solutions  are  alkaline  and  they  unite 
with  acids  to  form  salts.  Quinine  is  found  in  the  bark  of  the 
cinchona  tree.  It  is  used  as  a  medicine  in  the  treatment 
of  fevers.  Morphine  is  found  in  the  sap  of  unripe  poppies. 
When  this  sap  is  partially  dried  it  is  called  opium.  Cocaine 
is  a  crystalline  solid  present  in  cocoa  leaves  and  used  as  a 
local  anaesthetic.  Theine,  or  caffeine,  occurs  in  tea  and 
coffee.  Nicotine  is  a  very  poisonous  liquid  which  occurs 
in  the  leaves  of  the  tobacco  plant. 

SILICON 

Introduction.  Silicon  always  occurs  in  nature  in  the 
combined  state.  In  fact  it  is  very  difficult  to  prepare  the 
substance  in  the  free  form.  In  respect  to  chemical  rela- 
tions there  is  a  close  resemblance  between  carbon  and 
silicon.  Silicon  is  the  characteristic  element  of  the  inor- 
ganic or  mineral  kingdom  in  a  similar  way  that  carbon  is 
the  characteristic  element  of  the  plant  and  animal  kingdom. 

Distribution.  Silicon  is  the  most  abundant  element  next 
to  oxygen  and  constitutes  more  than  3^  of  the  earth's  crust. 
It  does  not  occur  free  in  nature,  but  its  compounds  are  very 
abundant  and  very  important.  Its  principal  compound  is 
silica  or  silicon  dioxide,  Si02.  Other  important  compounds 
are  silicates,  or  salts  of  silicic  acid.  Silica  and  silicates  form 
a  large  fraction  of  the  earth's  crust.  Silicon  is  found  in  the 
ash  of  most  plants  and  in  very  small  quantities  in  animal 
organisms.  It  is  not,  however,  regarded  as  essential  for 
either  plant  or  animal  life.  Its  presence  in  living  tissue  is 
probably  due  to  its  great  abundance  in  the  soil. 

Kieselguhr,  diatomaceous  earth,  is  an  interesting  sub- 
stance containing  about  90%  pure  silica  when  dry.     This 


134 


CHEMISTRY  OF  THE  FARM  AND  HOME 


material  is  formed  by  the  action  of  diatoms  in  bodies  of 
water.  The  silica  shell  of  these  plants  is  secreted  by  them 
and,  when  the  organism  dies,  is  deposited  in  large 
quantities.  The  deposits  of  kieselguhr  in  California  are  the 
largest  and  purest  of  any  that  are  known. 

Preparation.  Silicon  is  most  easily  prepared  by  heating 
powdered  quartz,  silica,  with  magnesium  powder.  The 
magnesium  reduces  the  silica  by  removing  the  oxygen.  An 
impure  form  of  sihcon  may  be  obtained  by  reduction  of 
quartz  with  carbon  in  an  electric  furnace. 

Properties.  The  element  silicon  resembles  carbon  in 
many  respects.  It  has  several  allotropic  forms,  correspond- 
ing to  those  of  carbon.  The  crystalline  form  is  very  hard 
and  is  inactive  towards  chemical  reagents.  The  amor- 
phous variety  has,  in  general,  properties  more  similar  to 
charcoal.  Silicon  melts  only  at  the  highest  temperature. 
It  is  not  affected  by  oxygen  at  ordinary  temperatures,  but 
when  strongly  heated  burns  with  great  brilliancy.  It  is  not 
attacked  by  acids  under  ordinary  conditions. 

Compounds  of  Silicon.  Silicon  forms  a  number  of  com- 
pounds of  the  same  general  type  that  carbon  forms.  These 
compounds,  though,  are  quite  different  in  their  properties 
from  the  corresponding  carbon  compounds. 

Silicides.  Silicon  combines  with  some  other  elements  to 
form   binary   compounds   called   silicides.     They   are   very 


Figure  37. — Cross-section  of  an  electric  furnace. 

stable  at  high  temperatures  and  are  usually  made  by  heating 
the  proper  ingredients  in  an  electric  furnace.  Carborundum 
is  the  most  familiar  and  probably  the  most  important  sub- 


SOME  OTHER  NON-METALS  135 

stance  of  this  character.  It  is  a  silicide  of  carbon,  and  is 
made  by  heating  coke  and  sand  in  an  electric  furnace  at 
3,500°C.  Figure  37  is  a  cross-section  view  of  the  type  of 
electric  furnace  in  which  carborundum  is  prepared.  The 
charge  of  sand  and  coke  is  placed  in  the  proper  position  and 
surrounded  by  the  walls  of  the  furnace.  A  powerful  elec- 
tric current  is  passed  through  the  mass  from  one  pole  to  the 
other.  After  cooling,  the  furnace  may  be  taken  apart  and 
the  products  removed.  Carborundum  consists  of  beautiful 
purplish  black  crystals  which  are  very  hard.  It  is  used  as 
an  abrasive.  Ferrosilicon  is  a  silicide  of  iron  which  is 
present  in  certain  kinds  of  steel. 

Silicon  Dioxide.  This  substance  occurs  in  a  great  variety 
of  forms  in  nature,  both  in  the  amorphous  and  the  crystal- 
hne  condition.  Quartz  is  a  variety  of  silica.  When  pure 
it  is  perfectly  transparent  and  colorless.  Some  colored 
varieties  of  quartz  are  the  amethyst,  rose  quartz,  and  smoky 
or  milky  quartz.  Other  varieties  of  this  substance  are 
onyx,  jasper,  opal,  agate  and  flint.  The  colored  varieties 
are  caused  by  the  presence  of  certain  impurities,  usually 
mineral  in  character,  but  organic  in  the  case  of  smoky 
quartz.  The  greater  proportion  of  sand  and  sandstone  is 
sihcon  dioxide.  Silica  is  also  found  in  the  hard  parts  of 
straw,  of  some  species  of  the  horse-tail  (equisetum)  and  the 
bamboo. 

Artificial  silica  is  an  amorphous  white  powder.  The 
crystallized  form  is  very  hard  and  has  a  density  of  2.6.  It 
is  insoluble  in  water  and  in  most  chemical  reagents  and 
requires  the  hottest  oxyhydrogen  flame  for  fusion.  With 
the  exception  of  hydrofluoric  acid,  acids  have  very  little 
effect  upon  it,  but  it  is  soluble  in  alkalies,  forming  silicates. 
In  the  form  of  whetstones  silica  is  used  for  grinding. 
The  clear  crystals  are  used  to  make  spectacles  and  optical 
instruments.     Pure  sand  is  used  in  glass  manufacture. 

Some  of  the  uses  of  kieselguhr  are  as  a  filtering  and 


136  CHEMISTRY  OF  THE  FARM  AND  HOME 

absorbing  medium  and  a  material  for  insulating,  for  deaden- 
ing sound  and  for  fire-proofing.  Fused  silica  or  quartz  is 
used  for  the  manufacture  of  laboratory  and  industrial  appa- 
ratus where  resistance  to  acids  and  a  small  coefficient  of 
expansion  are  desired.  Figure  38  shows  a  group  of  labora^ 
tory  utensils  made  from  vitreosilj  pure  fused  sihca. 


Figure   38. — Laboratory  apparatus  made   of  silica. 

Silicic  Acids.     Silicon  forms  two  simple  acids,  ortho  and 
meta.     Orthosilicic  acid  minus  water  gives  metasilicic  acid. 

H4Si04  —  H2O  -^  HaSiOa 
The  difference  between  these  is  that  the  ortho  con- 
tains a  molecule  of  water  more  than  the  meta.  Both  forms, 
when  heated,  give  silica  and  water.  There  are  many  complex 
acids  of  silicon,  which,  although  they  cannot  be  prepared 
in  the  pure  state,  occur  in  nature  as  salts  in  the  form  of 
rocks.  These  so-called  polysilicic  acids  may  be  regarded 
as  being  formed  when  several  molecules  of  orthosilicic  acid 
combine  with  loss  of  water. 


SOME  OTHER  NON-METALS 


137 


Mica  is  the  potassium  and  aluminium  salt  of  ortho- 
silicic  acid.  It  is  found  in  nature  in  the  form  of  large  sheets 
and  is  used  for  making  lamp  chimneys,  and  as  an  insulator 
for  electrical  apparatus.  Feldspar  is  a  mixed  potassium 
and  aluminium  salt  of  a  polysihcic  acid.  Kaolin  is  the 
aluminium  salt  of  a  polysilicic  hydrated  acid.  Some  of 
the  minerals  frequently  occur  mixed  together  as  regular 


Fi^'iirc  39. — A  section  of  spheroidal  granite. 

components  of  certain  igneous  rocks.  Granite  is  a  more 
or  less  coarse  mixture  of  quartz,  mica  and  feldspar.  Sand- 
stone is  composed  of  sand  cemented  together  by  clay  or 
lime  and  colored  brown  or  yellow  by  ferric  oxide.  The 
illustration  of  spheroidal  granite  (Figure  39)  shows  the 
manner  in  which  the  different  minerals  which  constitute 
the  granite  are  intimately  associated.  The  light  colored, 
glassy  masses  in  the  rock  are  quartz,  and  they,  with  the 
feldspar,  give  granite  its  characteristic  hard  resistant  qual- 
ities. 

SUMMARY 
Chlorine  is  a  very  active  element  and  always  occurs  in  nature 
in  the  combined  form.  Chlorides  are  common  and  of  great  importance, 
notably  common  salt.  Chlorine  is  prepared  by  oxidizing  hydrochloric 
acid  and  by  the  electrolysis  of  chlorides.  A  characteristic  property  of 
chlorine  is  its  attraction  for  hydrogen,   forming  hydrochloric  acid. 


138      CHEMISTRY  OF  THE  FARM  AND  HOME 

This  is  an  important  compound  of  chlorine  and  has  all  the  typical 
properties  of  an  acid.  The  principal  commercial  use  of  chlorine, 
namely  as  a  disinfecting  and  bleaching  agent,  is  due  to  this 
attraction  for  hydrogen,  as  nascent  oxygen  is  liberated  from  water 
by  the  process. 

Sulphur  occurs  in  both  the  free  and  combined  forms.  It  is  not 
only  an  important  constituent  of  plant  and  animal  life,  but  many  of 
its  compounds  are  valuable  for  commercial  purposes.  It  has  several 
allotropic  forms  which  differ  in  their  physical  properties  from  one 
another,  but  have  the  same  chemical  properties.  Sulphur  is  an  active 
element  chemically,  hydrogen  sulphide,  carbon  disulphide,  and  the  sul- 
phides and  sulphates  of  the  metals  being  examples  of  its  compounds. 
But  the  most  important  compounds  of  sulphur  are  the  oxides,  sulphur 
dioxide  and  trioxide,  and  sulphuric  acid.  These  substances  are  readily 
converted  into  one  another  by  oxidation  and  reduction  processes. 
Sulphuric  acid,  especially,  is  valuable  since  it  is  the  foundation  of  many 
chemical  industries. 

Phosphorus  always  occurs  in  the  combined  form,  since  it  is  a  very 
active  element.  There  are  two  allotropic  states  of  phosphorus,  the 
yellow  and  the  red.  These  differ  in  their  physical  properties  quite 
markedly,  but  have  the  same  chemical  characteristics.  The  principal 
uses  of  phosphorus  and  its  compounds  are  in  the  manufacture  of  match- 
es, phosphate  baking  powders  and  fertihzers. 

Carbon  is  an  element  of  special  importance  to  life.  It  is  widely 
distributed  in  many  thousand  compounds.  As  an  element  and  in 
its  various  compounds  it  is  of  the  greatest  value  to  mankind,  serving 
for  fuels,  food,  clothing,  building  materials,  industrial  articles  and 
pharmaceutical  preparations,  etc.  In  other  words,  carbon  enters 
into  every  phase  of  life  and  civilization.  There  are  more  carbon  com- 
pounds than  of  all  the  other  elements  put  together.  Some  of  the  prin- 
cipal classes  of  these  are  oxides,  carbonates,  hydrocarbons,  alcohols, 
acids,  esters,  ethers,  organic  bases  and  the  carbohydrates. 

Silicon  is  the  characteristic  element  of  most  rocks  and  minerals.  It 
never  occurs  free  in  nature,  but  may  be  prepared  in  the  elementary 
form  by  chemical  means.  It  has  several  allotropic  forms  and  is  very 
inert.  Some  of  its  principal  compounds  are  silica,  silicides  and  sili- 
cates. These  are  also  quite  resistant  to  chemical  change  and  are  of 
chief  interest  in  connection  with  the  study  of  the  earth's  crust.  Silica 
and  the  silicides  have  commercial  uses. 

These  elements,  together  with  oxygen,  hydrogen  and  nitrogen, 
are  the  most  important  non-metals  as  far  as  their  everyday  relations 
are  concerned. 


SOME  OTHER  NON-METALS  139 

QUESTIONS 

1.  State  how  chlorine,  sulphur,  phosphorus  and  silicon  occur 
in  nature. 

2.  Name  some  tests  by  which  it  is  possible  to  distinguish  be- 
tween chlorine  and  hydrochloric  acid. 

3.  Explain  how  chlorine  bleaches. 

4.  Compare  properties  of  hydrochloric  acid  and  sulphuric  acid. 

5.  Discuss  the  relative  commercial  importance  of  hydrochloric 
acid  and  sulphuric  acid. 

6.  If  hydrogen  sulphide  were  a  hquid,  would  it  be  necessary 
to  modify  the  method  of  preparation? 

7.  What  are  the  chief  differences  between  the  properties  of 
the  yellow  and  the  red  phosphorus? 

8.  Discuss  the  function  of  phosphorus  in  plants  and  animals. 

9.  Discuss  the  relation  of  carbon  dioxide  to  plant  and  animal  life. 

10.  In  what  way  do  the  following  substances  differ  from  one 
another:  peat,  Hgnite  and  anthracite? 

11.  How  could  you  judge  the  relative  purity  of  different  forms 
of  carbon? 

12.  How  can  you  tell  the  difference  between  soft  and  hard  coal; 
between  bone  black  and  lamp  black? 

13.  What  are  some  of  the  differences  in  the  properties  of  carbon 
monoxide  and  carbon  dioxide? 

14.  When  sugar  is  heated  sufficiently  to  char  it,  what  substances 
are  formed  and  what  elements  are  indicated? 

15.  Name  the  elements  so  far  studied  having  allotropic  forms. 

16.  What  substances  studied  are  used  as  bleaching  agents? 
To  what  is  the  bleaching  action  due  in  each  case? 

17.  For  each  of  the  following  gases  name  a  property  which 
will  distinguish  it  from  the  other  gases  given:  hydrogen,  oxygen, 
chlorine,  nitrogen,  carbon  dioxide,  ammonia. 

18.  Suppose  four  jars  of  gas  were  given  to  you,  one  containing 
carbon  dioxide,  another  nitrogen,  the  third  hydrogen  and  the  last 
chlorine.     By  what  tests  could  you  identify  the  contents  of  each  jar? 

19.  Write  the  equation  illustrating  the  neutralization  of  hydro- 
chloric acid  by  potassium  hydroxide;  of  hydrochloric  acid  by  calcium 
hydroxide. 

20.  State  what  gases  you  have  studied  can  be  identified  with- 
out the  use  of  chemical  tests  and  how. 

21.  Make  a  table  of  any  six  gases  studied  showing  five  or  more 
of  the  physical  and  chemical  properties  by  which  these  substances 
may  be  identified. 

22.  What  commercial  uses  are  made  of  ammonia;  of  the  dif- 
ferent forms  of  carbon? 

23.  What  is  meant  by  the  terms  inert  [substance,  destructive 
distillation,   catalytic  agent? 

24.  Name  the  following  substances  from  their  description: 
(a)  A  gas,  heavier  than  air,  has  color,  odor,  and  taste,  does  not  burn 
but  is  very  active,  combining  with  other  substances  by  simple  contact 
with  them,  (b)  A  liquid,  has  sharp  odor  and  taste,  turns  litmus  red, 
attacks  metals  and  minerals,  and  gives  off  a  greenish  yellow  gas  when 
treated  with  manganese  dioxide. 


CHAPTER  V 
A  FEW  IMPORTANT  METALS 

The  metals  are  a  class  of  elements  which  have  certain 
properties  in  common.  They  are  sometimes  called  the 
base-forming  elements,  since  their  hydroxides  are  bases. 
The  distinction  between  a  metal  and  a  non-metal  is  not 
very  sharp,  since  the  hydroxides  of  a  number  of  elements 
may  act  as  both  bases  and  acids. 

Occurrence.  A  few  metals,  such  as  gold,  platinum,  and 
copper,  occur  in  the  free  form  in  nature.  They  are  usually 
found  as  compounds,  of  which  the  oxides,  silicates,  car- 
bonates, sulphides,  and  sulphates  are  the  most  abundant 
forms.  The  term  mineral  is  generally  applied  to  all  inor- 
ganic substances  occurring  in  nature.  An  ore  is  a  mineral 
substance  from  which  a  useful  substance,  as  iron,  can  be 
extracted. 

Extraction  of  Metals.  The  process  of  extracting  a  metal 
from  its  ores  is  called  the  metallurgy  of  the  metal.  While 
each  metal  has  special  processes  of  its  own,  there  are  several 
methods  of  general  application  which  are  employed. 

(1)  Reduction  of  an  oxide  with  carbon.  When  oxides  of 
metals  are  heated  with  carbon,  the  latter  combines  with 
the  oxygen  forming  carbon  monoxide  and  carbon  dioxide 
which  pass  off  as  gases  and  leave  the  metal  free.  The 
principle  of  this  extraction  has  already  been  demonstrated 
in  the  experiment  upon  copper  oxide  and  carbon.  The 
importance  of  this  method  is  shown  by  its  application  to 
the  reduction  of  iron  from  its  oxides.  If  the  ore  is  not 
already  in  the  form  of  an  oxide,  it  can  be  roasted  or  heated 
in  a  current  of  air.  In  this  way,  sulphides  are  changed  to 
oxides  and  the  sulphur  is  driven  off  as  sulphur  dioxide. 

140 


A  FEW  IMPORTANT  METALS  141 

Simple  direct  heating  is  sufficient  in  some  cases  to  change 
carbonates  and  hydroxides  into  the  oxides. 

(2)  Reduction  of  an  oxide  with  aluminium.  It  is  im- 
possible to  reduce  oxides  of  all  the  metals  with  carbon. 
In  such  cases  aluminium  may  be  used.  The  aluminium 
has  a  strong  attraction  for  oxygen  and  abstracts  it  from 
the  metallic  oxide.  This  is  sometimes  called  the  Gold- 
schmidt  method,  after  its  inventor.  A  practical  applica- 
tion will  be  seen  under  the  case  of  thermite. 

(3)  Electrolysis.  The  use  of  the  electric  current  has 
made  possible  both  experimental  and  commercial  prepara- 
tion of  the  metals  which  could  not  formerly  be  easily  sepa- 
rated. The  metal  is  prepared  from  its  compound  either  by 
passing  the  electric  current  through  a  solution  of  a  suitable 
salt  of  the  metal  or  through  a  fused  salt  of  the  metal.  The 
latter  is   usually  deposited   upon  the   cathode. 

When  a  current  of  electricity  is  passed  through  conducting 
solutions,  the  latter  are  called  electrolytes.  The  substance  in 
solution  which  is  electrolyzed  is  supposed  to  be  broken  up  into 
two  parts,  or  ions,  the  cation  carrying  a  positive  charge  of  elec- 
tricity and  going  to  the  negative  pole,  and  the  anion  carrying 
a  negative  charge  and  going  to  the  positive  pole.  The  poles 
are  called  cathode  and  anode  respectively.  An  ion  is  an  atom 
of  an  element  plus  an  electrical  charge.  Or,  an  ion  may  be 
a  radicle,  or  group  of  atoms,  plus  an  electrical  charge. 

THE  ALKALI  METALS 

Introduction.  The  name  alkali  metals  is  applied  to  a 
group  or  family  of  elements,  because  the  hydroxides  of 
sodium  and  potassium,  which  belong  to  the  group,  have 
long  been  called  alkalies.  These  metals  do  not  occur  free 
in  nature,  but  their  compounds  are  widely  distributed. 
Sodium  and  potassium,  especially,  occur  in  abundance  in 
natural  waters,  in  salt  beds  and  in  rocks.  The  metals  are 
conveniently  prepared  by  electrolytic  methods. 


142  CHEMISTRY  OF  THE  FARM  AND  HOME 

The  alkali  metals  almost  always  act  as  univalent  elements 
in  the  formation  of  compounds.  With  the  exception  of 
lithium  they  form  very  few  insoluble  compounds.  The 
compounds  of  sodium  and  potassium  are  so  similar  in  their 
properties  that  they  can  be  used  interchangeably  for  most 
purposes.  Sodium  compounds  are  cheaper,  however,  and 
therefore,  are  used  if  possible.  Sometimes  certain  prop- 
erties of  a  sodium  compound  are  such  that  the  substance 
cannot  be  used  for  a  specific  purpose.  Then  the  correspond- 
ing potassium  compound  is  used. 

SODroM 

Distribution.  Large  deposits  of  sodium  chloride,  com- 
mon salt,  have  been  found  in  various  portions  of  the  world. 
Natural  waters,  especially  the  ocean,  and  many  lakes  and 
springs  contain  large  amounts  of  it.  Sodium  is  also  a  con- 
stituent of  many  rocks  and  consequently  is  present  in  the 
soil  formed  from  these.  Though  it  does  not  seem  to  be 
necessary  for  plant  life,  it  is  present  in  plants,  especially 
seaweeds  and  other  marine  plants.  Besides  common  salt 
deposits,  sodium  is  found  in  the  form  of  nitrate,  carbonate, 
borate  and  the  double  fluoride  of  aluminium  and  sodium. 

Preparation.  Sodium  may  be  prepared  by  reducing 
the  carbonate  with  carbon.  The  best  method  at  present 
is  to  decompose  fused  sodium  hydroxide  or  sodium  chlo- 
ride by  means  of  the  electric  current.  The  process  is  car- 
ried on  extensively  at  Niagara  Falls. 

Physical  Properties.  Sodium  is  a  silver  white  metal 
about  as  heavy  as  water.  It  is  so  soft  that  it  can  be  easily 
compressed  into  any  shape  desired. 

Chemical  Properties.  This  element  is  very  active  chem- 
ically, combining  with  most  of  the  non-metallic  elements 
such  as  oxygen  and  chlorine  with  great  energy.  This  activ- 
ity is  shown  by  the  rapid  tarnishing  of  the  metal  when 
exposed  to  the  air  on  account  of  the  formation  of  the  sodium 


A  FEW  IMPORTANT  METALS  143 

oxide.  In  order  to  preserve  the  substance  in  the  metalHc 
form,  the  sodium  is  kept  in  kerosene  which  contains  no  water 
or  oxygen.  Sodium  not  only  has  a  strong  attraction  for 
free  oxygen  and  chlorine  but  it  also  is  able  to  abstract  these 
elements  from  their  compounds.  Such  a  reaction  has 
already  been  demonstrated  in  the  preparation  of  hydrogen 
by  bringing  sodium  in  contact  with  water. 

Compounds  of  Sodium.  Sodium  hydroxide^  caustic 
soda,  lye,  NaOH.  This  important  substance  may  be  pre- 
pared in  a  number  of  ways.  It  will  be  recalled  that,  in  the 
preparation  of  hydrogen  by  the  action  of  sodium  upon  water, 
the  character  of  the  liquid  remaining  was  quite  different  after 
the  reaction  than  before.  It  was  soapy  to  the  touch,  bitter 
to  the  taste,  and  alkaline  to  litmus.  The  liquid  was  dilute 
sodium  hydroxide,  and  this  method  is  the  simplest  for  pre- 
paring the  compound.  Commercially,  the  electrolytic 
methods  are  the  most  important  at  the  present  time.  In 
the  Castner  process  a  solution  of  common  salt  is  electro- 
lyzed,  in  the  Acker  process  fused  sodium  chloride  is  exposed 
to  the  action  of  the  electric  current.  In  both  cases  chlo- 
rine is  evolved  and  is  drawn  away  through  pipes  to  the 
bleaching  powder  chambers.  The  sodium  which  is  pro- 
duced at  the  other  pole  is  alloyed  with  mercury  or  lead 
and  by  ingenious  devices  is  brought  in  contact  with  water 
in   another   chamber   than   the   electrolytic   cell. 

In  the  Castner-Kellner  apparatus.  Figure  40,  which  serves 
for  the  manufacture  of  either  sodium  or  potassium  hydrox- 
ides, the  two  end  compartments  are  filled  with  a  brine  of 
sodium  or  potassium  chlorides  and  contain  graphite  elec- 
trodes, the  positive  poles.  The  central  compartment  con- 
tains the  caustic  alkali  and  an  iron  electrode,  the  negative 
pole.  The  positive  current  enters  by  the  anodes  and  the 
chlorine  is  attracted  and  liberated  there.  The  sodium  or 
potassium  is  discharged  upon  a  layer  of  mercury  which 
covers  the  whole  floor  of  the  box  and  forms  an  amalgam. 


144 


Ohemtstry  of  the  farm  and  home 


The  layer  of  mercury  extends  beneath  the  partitions  and  a 
sHght  rocking  motion  given  to  the  cell  by  the  cam  (C) 
causes  the  amalgam  to  flow  beneath  the  partition  into  the 
central  compartment.  Here  the  sodium  is  attracted  to  the 
cathode  and  when  liberated  there  unites  with  the  water, 
forming  sodium  hydroxide  and  hydrogen.  The  sodium 
hydroxide  in  the  solution  can  be  run  off  and  evaporated 


73 er 

Figure  40. — Apparatus  for  the  manufacture  of  caustic  alkalies. 

to  the  solid  material.  Some  of  the  compound  is  still  man- 
ufactured by  the  older  process  of  treating  sodium  carbon- 
ate with  water  slakedlime. 

Sodium  hydroxide  is  a  white,  crystalline,  brittle  sub- 
stance which  absorbs  water  and  carbon  dioxide  rapidly  from 
the  air.  It  is  a  very  corrosive,  or  caustic,  substance  and 
has  a  disintegrating  action  upon  most  animal  and  vegetable 
tissues.  It  is  a  strong  base  or  alkali  and  is  used  in  the 
household  under  the  name  of  lye  for  cleansing  purposes. 
It  has  numerous  industrial  uses  an  example  of  which  is  its 
application  to  soap  making. 

Sodium  chloride,  common  salt,  NaCl.  This  compound 
is  very  widely  distributed  in  nature.  It  constitutes  about 
3H%  of  the  water  of  the  ocean.  In  other  words,  about  90% 
of  the  soluble  salts  in  the  salt  water  is  sodium  chloride. 
Thick  layers  of  the  salt,  possibly  deposited  at  one  time  by 
the  evaporation  of  salt  water,  are  found  in  many  places. 
New  York,  Michigan,  Ohio,  and  Kansas  have  important 


A  FEW  IMPORTANT  METALS  145 

salt  deposits.  The  substance  is  mined,  especially  if  in  the 
form  of  rock  salt,  or  a  strong  brine  is  pumped  from  deep  wells 
sunk  into  the  deposits  and  is  then  evaporated  until  the 
salt  crystallizes  out.  In  warm  climates  salt  water  of 
the  sea  is  allowed  to  overflow  tracts  of  land,  then  re- 
tained there  by  dikes  and  evaporated  by  the  heat  of  the  sun. 

Enormous  quantities  of  salt  are  produced  each  year  for 
commercial  purposes.  As  it  is  the  most  abundant  compound 
of  both  sodium  and  chlorine,  it  serves  as  the  starting  point 
for  nearly  all  compounds  containing  those  elements.  Many 
substances  of  the  greatest  importance  to  mankind  are  in 
this  list.  Soap,  glass,  hydrochloric  acid,  soda  and  bleaching 
powder  are  a  few  examples.  Small  quantities  of  salt  are 
essential  to  human  and  animal  life.  Pure  salt  does  not  ab- 
sorb water.  Ordmary  table  salt  contains  impurities  such  as 
chlorides  of  calcium  and  magnesium.  The  presence  of  these 
compounds  is  responsible  for  the  fact  that  table  salt  becomes 
moist  when  exposed  to  the  air. 

Sodium  sulphate,  Glauber's  salt,  Na2S04,  is  extensively 
used  in  the  manufacture  of  sodium  carbonate  and  glass. 
Small  quantities  are  used  in  medicine. 

Sodium  thiosulphate,  hyposulphite,  hypo,  Na2S203.  This 
substance  is  used  in  photography  to  fix  the  negative  after 
development.  It  dissolves  the  undecomposed  silver  bro- 
mide and  clears  the  plate.  It  is  also  used  in  the  bleaching 
industry  to  absorb  the  excess  of  chlorine  left  upon  the 
fabrics  and  thus  prevent  injury  to  them. 

Sodium  carbonate,  sal  soda,  washing  soda,  Na2C03. 
This  important  compound  may  be  prepared  by  two  different 
methods.  The  so-called  Leblanc  process  is  the  older  and 
the  less  satisfactory  one.  It  involves  considerable  expense 
for  fuel,  there  is  a  loss  of  much  matter,  and  the  by-products, 
with  the  exception  of  hydrochloric  acid,  are  not  valuable. 
The  production  of  this  hydrochloric  acid  is  the  only  salva- 
tion of  the  method  and  is  responsible  for  its  successful  com- 

10— 


146  CHEMISTRY  OF  THE  FARM  AND  HOME 

petition  with  the  other  process,  the  Solvay  method.  The 
Leblanc  process  involves  several  distinct  reactions.  Com- 
mon salt  is  treated  with  sulphuric  acid  and  converted  to 
the  sulphate.  This  is  next  reduced  to  sodium  sulphide  by 
carbon.  The  sulphide  is  finally  changed  to  carbonate  by 
heating  with  calcium  carbonate.  The  process  is  carried 
on  upon  the  hearth  of  a  reverberatory  furnace,  where  the 
heated  gases  from  the  fire  are  deflected  from  the  roof  upon 
the  materials.  Figure. 41  shows  the  cross-section  of  such  a 
furnace.     The  equations  for  the  reactions  are  shown  below. 

NaCl  +  H2SO4  -^  NaHS04  +  HCl 
NaCl  +  NaHS04  ->  Na2S04  +  HCl 
Na2S04  +  2  C  ->  Na2S  +  2  CO2 
Na2S  +  CaCOs  ->  Na2C03  +  CaS 

The  Solvay  process  is  the  more  modern  and  the  more 
economical.  The  principle  of  this  process  is  to  pass  am- 
monia gas  and  carbon  dioxide  gas  into  a  strong  solution  of 
common  salt.  Sodium  bicarbonate,  NaHCOs,  is  formed  in 
this  way  and,  being  sparingly  soluble  under  the  conditions, 
is  precipitated.  It  may  be  changed  into  sodium  carbonate 
by  heating.  In  the  Solvay  method  there  is  only  one  waste 
by-product,  calcium  chloride.  The  ammonia  gas  is  used  in 
a  constant  round  with  only  a  slight  loss.  Calcium  carbon- 
ate furnishes  the  carbon  dioxide  and  the  quicklime  required 
in  the  process.  The  Solvay  process  is  an  excellent  illus- 
tration of  a  chemical  manufacturing  process  where  there 
is  little  loss  of  material  in  the  reacting  chemicals.  The 
equations  representing  the  ammonia-soda  process  are  as 
follows: 

NaCl  +  NH4HCO3  -^  NaHCOs  +  NH4CI 
2  NaHCOs  -^  Na2C03  +  H2O  +  CO2 

Sodium  carbonate  forms  large  crystals  with  ten  mole- 
cules of  water  of  crystallization.     It  is  mildly  alkaline  and 


A  FEW  IMPORTANT  METALS 


147 


is  used  for  laundry  purposes  under  the  name  of  washing 
soda.  Commercially  it  is  used  in  the  manufacture  of  glass, 
soap,  and  many  chemical  reagents.  Agriculturally  it  is  of 
interest,  since  it  is  one  of  the  substances  which  is  responsi- 
ble for  the  so-called  black  alkah  effect  in  soils. 

Sodium  bicarbonate,  baking  soda,  saleratus,  NaHCOa- 
This  compound  is  prepared  directly  in  the  Solvay  process. 
Its  properties  are  similar  to  those  of  the  sodium  carbonate. 
The  principal  use  of  the  bicarbonate  is  in  the  preparation 
of  baking  powders,     As  it  is  a  mild  alkah  and  contains 

carbon  dioxide,  when 
brought  in  contact  with 
an  acid  reacting  sub- 
stance in  the  presence 
of  water,  there  is  a  reac- 
tion and  carbon  dioxide 
is  liberated.  This  gas 
forces  its  way  through  the 
dough  and  makes  it  por- 
ous and  light. 

Sodium  nitrate,  Chile 
saltpetre,  NaNOa.  Sodium  nitrate  is  found  in  nature  in 
arid  regions,  probably  formed  by  the  decay  of  organic 
substances  containing  nitrogen,  in  the  presence  of  air 
and  sodium  salts.  The  largest  deposits  are  in  Chile, 
though  smaller  deposits  have  been  reported  in  Cali- 
fornia and  Nevada.  The  commercial  substance  is  pre- 
pared from  the  natural  raw  material  by  treatment  with 
water.  The  nitrate  dissolves  and  the  earthy  impurities 
settle  out.  The  solution  is  then  evaporated  until  the  nit- 
rate crystallizes  out.  Sodium  nitrate  is  of  especial  impor- 
tance for  two  commercial  uses,  the  preparation  of  explosives 
and  as  sl  fertilizer.  In  the  first  instance  it  is  the  raw  material 
from  which  nitric  acid  and  potassium  nitrate  are  prepared. 
In  the  second  place  it  may  be  used  directly  as  a  nitrogenous 


Figure  41. 


-Cross-section  of  a  reverberatory 
furnace. 


148  CHEMISTRY  OF  THE  FARM  AND  HOM^ 

fertilizer  or  in  mixed  fertilizers.  In  either  case  it  is  a  val- 
uable source  of  nitrogen,  since  nitrogen  in  this  form  is  im- 
mediately available  to  plants. 

Sodium  tetraborate,  borax,  Nar2B407.  Borax  is  found  in 
some  arid  countries,  as  southern  California.  It  is  now 
made  commercially  from  the  mineral  colemanite,  which  is  the 
calcium  salt  of  a  complex  boric  acid.  It  has  the  peculiar 
property,  when  heated,  of  swelling  to  a  great  mass  on  account 
of  the  expulsion  of  the  water  of  crystallization  and  then  melt- 
ing to  a  clear  glass.  This  glass  easily  dissolves  many  me- 
tallic oxides  and  is,  therefore,  used  as  a  flux  in  soldering  to 
clean  the  surface  of  the  metals.  It  is  also  extensively  used 
as  a  constituent  of  enamels  and  glazes  for  both  metal  ware 
and  pottery.  In  the  household  it  acts  as  a  mild  alkali  and 
is  used  to  soften  water,  to  preserve  meats,  and  for  a  number 
of  other  less  important  appUcations. 

POTASSIUM 

Introduction.  Potassium  is  a  metal  which  much  resem- 
bles sodium  in  its  properties.  Like  sodium  it  never  occurs 
free  in  nature,  though  its  compounds  are  fairly  widely  distrib- 
uted. Potassium  compounds  are  important  for  several  rea- 
sons. First,  they  are  valuable  for  use  in  agriculture  as  fertiliz- 
ers for  the  potassium  contained  in  them.  Second,  they  are  of 
service  in  the  arts  on  account  of  the  other  constituents 
contained  in  them.  Potassium  compounds  are  generally 
more  costly  than  the  corresponding  sodium  compounds. 
The  chief  reason  is  because  the  amount  of  easily  accessible 
potassium  compounds  is  far  less  than  that  of  easily  acces- 
sible sodium  compounds.  It  is  true,  however,  that  the 
aggregate  amount  of  these  two  substances  in  the  earth's 
crust  seems  to  be  about  the  same. 

Distribution.  Potassium  is  widely  distributed  in  combi- 
nation with  other  substances,  never  in  the  free  state.  It 
occurs  in  many  minerals  and  rocks.     Orthoclase,  a  variety 


A  FEW  IMPORTANT  METALS  14^ 

of  feldspar,  contains  14%  of  potassium.  Rocks  like  granite 
contain  some  of  these  minerals.  There  are  some  natural 
deposits  of  salts  which  are  rich  in  soluble  potassium  com- 
pounds. The  so-called  Stassfurt  deposits  in  Prussia  are  the 
best  known  source  of  potassium  compounds  which  are  used 
for  various  purposes.  Compounds  of  potassium  exist  in 
minute  quantities  in  soils,  being  derived  from  the  minerals 
and  rocks  of  which  the  soil  is  composed.  Natural  waters, 
such  as  certain  mineral  springs  and  the  Dead  Sea  and  the 
ocean,  contain  very  small  quantities  of  potassium.  Plants 
have  the  power  of  selecting  potassium  salts  from  the  soil. 
The  ashes  of  these  plants  contain  the  potassium,  principally 
in  the  form  of  potassium  carbonate.  Wood  ashes,  especially, 
are  important  for  the  potassium  they  contain.  Some 
animal  products  have  considerable  potassium  in  their  struc- 
ture.    The  greasy  material  of  sheep's  wool  is  an  example. 

Preparation.  Potassium  can  be  prepared  in  the  same 
manner  that  the  element  sodium  is,  either  by  heating  a  mix- 
ture of  potassium  carbonate  and  charcoal  or  by  electrolysis 
of  the  chloride  of  potassium.  The  latter  method  is  the  one 
most  generally  used  at  the  present  time. 

Physical  Properties.  Potassium  is  a  silvery-white  metal. 
It  is  soft,  easily  cut  with  a  penknife,  and  is  the  lightest 
metal  except  lithium.  It  melts  and  volatilizes  very  readily 
under  the  influence  of  a  moderate  heat. 

Chemical  Properties.  Potassium  is  very  active,  even 
more  energetic  in  its  action  upon  other  substances  than 
sodium.  It  reacts  with  the  oxygen  of  the  air  so  quickly  that 
it  is  difficult  to  see  the  bright  clean  surface  of  the  metal  when 
it  is  cut.  It  also  decomposes  water  very  readily,  and  gives 
enough  heat  to  set  fire  to  the  hydrogen  evolved  by  the  re- 
action. For  this  reason  it  is  always  kept  under  kerosene 
or  gasoline. 

Compounds  of  Potassium.  Potassium  hydroxide,  caustic 
potash,    KOH.     This    substance    is    prepared  by  methods 


150      CHEMh^TRY  OF  THE  FARM  A^^D  HOME 

which  are  the  same  as  those  used  for  the  preparation  of 
sodium  hydroxide.  It  resembles  the  latter  substance  very 
closely  in  its  properties  and  is  replaced  by  the  sodium  com- 
pound for  commercial  uses  on  account  of  the  lesser  cost  of 
caustic  soda. 

Potassium  nitrate,  saltpetre  and  nitre,  KNO3.  This 
compound  is  found  in  certain  parts  of  India,  as  crusts  in 
the  earth.  It  also  occurs  in  soils  to  a  small  extent.  It  was 
formerly  made  by  decomposing  animal  refuse  in  the  open 
air  in  the  presence  of  wood  ashes.  Potassium  nitrate  is 
now  largely  made  by  a  reaction  between  sodium  nitrate 
and  potassium  chloride,  both  natural  salts.  Potassium 
nitrate  is  a  colorless  salt  which  forms  very  large  crystals. 
It  is  stable  in  the  air,  and  when  heated  it  is  a  good  oxidizing 
agent,  giving  up  part  of  its  oxygen  quite  readily. 

The  chief  use  of  potassium  nitrate  is  in  gunpowder  and 
fireworks.  Enormous  quantities  of  it  are  used  in  blasting, 
powder  as  well  as  gunpowder.  Some  saltpetre  is  also  used 
for  the  preservation  of  salted  meats.  The  use  of  this  com- 
pound in  the  explosives  depends  upon  the  nitrate  part  of 
the  compound  and  not  upon  the  potassium.  But  the  cor- 
responding sodium  nitrate  has  the  unfortunate  property 
of  absorbing  water  from  the  atmosphere  and  that  of  course 
prevents  its  use  in  the  powders. 

Uses  of  Potassium.  The  most  important  use  of  potas- 
sium compounds  is  undoubtedly  in  connection  with  agri- 
culture. Since  potassium  is  one  of  the  elements  absolutely 
necessary  for  plant  life,  and  since  it  is  likely  to  be  deficient 
in  certain  soils,  the  element  must  be  supplied  to  those 
soils  before  their  maximum  cropping  capacity  can  be  attained 
Soluble  potassium  salts,  such  as  the  sulphate,  the  chloride, 
the  carbonate,  and  occasionally  the  nitrates,  are  used  for 
this  purpose. 

Potassium  compounds  are  largely  used  for  industrial 
purposes,  but  in  these  cases,  with  certain  exceptions,  the 


A  FEW  IMPORTANT  METALS  151 

presence  of  the  potassium  is  merely  incidental.  The  com- 
pound employed  is  useful  on  account  of  the  other  element 
or  elements  present.  The  most  striking  example  of  this 
is  the  use  of  potassium  nitrate  in  explosives,  instead  of  the 
cheaper  sodium  nitrate.  Another  instance  is  the  use  of 
potassium  dichromate  instead  of  sodium  dichromate  in 
certain  manufacturing  processes.  This  is  because  the  potas- 
sium compound  is  more  easily  secured  in  the  pure  form  than 
the  sodium  compound. 

CALCroM 

Introduction.  Calcium  compounds  exist  in  nature  in 
comparative  abundance.  The  preparation,  properties,  and 
uses  of  quicklime  have  been  known  since  the  first  century 
of  our  era.  Calcium  occurs  in  a  number  of  different  com- 
pounds, all  of  which  are  very  useful  to  man.  Building 
stones,  and  artificial  building  substances,  are  secured  from 
natural  calcium  compounds.  These  compounds  also  have 
important   agricultural    uses. 

Distribution.  Calcium  never  occurs  in  nature  in  the 
free  form.  It  is,  however,  one  of  the  principal,  constituents 
of  many  minerals  and  rocks.  Calcium  carbonate  is  probably 
the  most  important  compound  of  this  element.  It  exists 
in  nature  in  a  number  of  different  forms,  such  as  limestone, 
marble,  chalk,  the  shells  of  shell-fish,  etc.  Limestone  is 
composed  largely  of  calcium  carbonate,  the  amount  depend- 
ing upon  the  purity  of  the  substance.  Another  important 
source  of  calcium  is  the  sulphate,  the  natural  form  being 
called  gypsum.  This  substance  is  widely  distributed  in 
natural  waters,  in  soils,  and  in  salt  deposits."  Calcium 
silicate  is  a  common  constituent  of  many  minerals  and  rocks. 
Calcium  phosphate  occurs  in  certain  amounts  in  the  soil, 
and  in  deposits.  From  all  these  minerals  calcium  finds 
its  way  into  natural  waters  and  the  soil.  It  is  also  taken  up 
by  plants  and  is  an  essential  part  of  the  mineral  portion  of 


152  CHEMISTRY  OF  THE  FARM  AND  HOME 

plant  life.  The  bones  of  animals  are  composed  of  calcium 
phosphate  in  great  part.  It  is  easily  seen,  therefore,  that 
calcium  is  widespread  in  nature  and  is  very  important  for 
all  life  processes. 

Preparation.  Calcium  may  be  prepared  by  the  electro- 
lysis of  certain  of  its  compounds,  such  as  fused  calcium 
chloride. 

Properties.  Calcium  is  a  gray  metal,  considerably 
heavier  and  harder  than  sodium.  It  oxidizes  on  the  surface 
in  slightly  moist  air.  It  readily  decomposes  water  at  ordi- 
nary temperatures,  but  the  action  is  not  violent  enough  to 
heat  the  water  and  melt  the  metal.  Calcium  hydroxide 
and  hydrogen  are  the  products  of  this  reaction.  There  are 
no  important  uses  for  the  metal  at  the  present  time,  but  it 
may  prove  valuable  in  the  future. 

Compounds  of  Calcium.  Calcium  oxide,  quicklime,  CaO. 
This  substance  is  readily  produced  by  heating  any  form  of 
the  carbonate  in  a  properly  constructed  furnace.  The 
limestone,  or  other  raw  material,  undergoes  a  loss  of  weight 
and  changes  its  properties.  By  this  method  100  parts  of 
limestone  give  only  56  parts  of  quicklime,  the  difference 
being  the  carbon  dioxide  which  is  evolved  by  the  heat 
treatment. 

CaCOs  -^  CaO  +  CO2. 

The  manufacture  of  quicklime  is  a  most  important  indus- 
try on  account  of  the  extensive  use  of  the  substance  in 
mortars  and  cements.  The  furnaces  in  which  the  lime- 
stone is  strongly  heated  are  called  kilns.  The  older  style  of 
kiln  had  to  be  fired  and  cooled  as  each  charge  of  limestone 
was  changed  to  quicklime.  The  newer  lime-kiln  is  so 
constructed  that  the  process  is  a  continuous  one,  limestone 
being  charged  in  at  the  top  of  the  kiln  as  fast  as  quick- 
lime is  removed  from  the  bottom.  A  number  of  fire  boxes 
are  built  around  the  base  of  the  kiln  and  the  hot  gases  are 
passed  up  through  the  mass  of  limestone.     The  carbon  dioxide 


A  FEW  IMPORTANT  METALS  153 

liberated  in  the  process  may  be  conveyed  away  through  pipes 
for  appropriate  uses. 

Pure  Hme  is  a  white  amorphous  substance.  The  char- 
acteristic property  of  quickhme  is  its  action  upon  water. 
It  evolves  a  great  deal  of  heat,  sufficient  in  some  cases  to 
set  fire  to  combustible  material  with  which  it  may  be  in 
contact.  This  process  is  commonly  called  slaking.  Cal- 
cium hydroxide  is  the  result  of  the  reaction. 

CaO  +  H2O  ->  Ca(0H)2. 
Lime  not  only  combines  with  free  water  in  bulk,  but  it 
also  absorbs  moisture  from  the  atmosphere.  For  this 
reason  it  is  sometimes  used  to  help  remove  the  dampness 
from  cellars.  Quicklime  also  has  a  strong  attraction  for 
carbon  dioxide  and  absorbs  this  gas  from  the  atmosphere, 
thereby  returning  to  its  original  form  of  calcium  carbonate. 
CaO  +  CO2  ->  CaCOs. 

This  double  action  of  lime  in  absorbing  moisture  and 
carbon  dioxide  from  the  atmosphere  is  called  air-slaking. 
Both  calcium  hydroxide  and  calcium  carbonate  are  results 
of  this  process  and  the  air-slaked  lime  is  a  white  powder 
which  will  no  longer  slake  with  water.  Another  characteris- 
tic property  of  quicklime  is  that  when  heated  intensely  as 
in  the  oxyhydrogen  flame,  it  gives  a  brilliant  white  light, 
commonly  called  the  lime  light.  This  light  has  been  very 
useful  for  stereopticon  lectures  and  theatrical  purposes, 
but  is  being  rapidly  supplanted  by  the  increasing  use  of 
electricity. 

The  chief  use  of  quicklime  is  for  preparation  of  mor- 
tar and  cement.  For  these  purposes  the  lime  is  first 
slaked  with  water  and  then  mixed  with  sand  in  the  pro- 
portion of  one  part  of  lime  to  three  of  sand.  When  the  mix- 
ture is  used  as  mortar  for  laying  bricks  and  stone,  a 
chemical  change  takes  place  gradually,  requiring  sometimes 
many  years  for  its  completion.  This  is  commonly  called  the 
drying  ov  setting  of  mortar  and  involves  the  gradual  expul- 


154  CHEMISTRY  OF  THE  FARM  AND  HOME 

sion  of  the  water  used  in  making  the  slaked  Hme.  Carbon 
dioxide  is  absorbed  by  the  Hme,  giving  calcium  carbonate 
which  binds  the  particles  of  sand  together.  The  sand  gives 
body  to  the  mortar,  prevents  too  much  shrinkage,  and  makes 
the  mortar  porous  so  that  the  change  into  the  carbonate 
can  take  place  evenly  through  the  mass. 

Cement  is  another  important  building  material  which 
is  made  with  the  aid  of  lime.  Limestone,  clay  and  sand 
are  heated  until  the  mixture  is  partly  fused,  and  the  clinker 
then  ground  to  a  fine  powder.  When  this  cement  is  mois- 
tened with  water,  it  sets  to  a  hard  stone-like  mass.  The 
setting  of  cement  is  due  to  the  absorption  of  water  and  not 
to  the  absorption  of  carbon  dioxide.  The  process  can  take 
place  even  under  water,  so  that  cement  is  particularly 
valuable  for  that  kind  of  construction.  It  is  becoming 
more  and  more  useful  for  building  purposes  and  can  be  used 
in  a  great  variety  of  ways.  It  is  often  used  in  place  of 
mortar  for  laying  bricks.  Mixed  with  crushed  stone  and 
sand  it  forms  concrete  which  is  used  in  foundation  work. 
It  is  also  used  for  making  artificial  stones  or  cement  blocks, 
stone  walks,  and  in  fact  any  building  material  which  was 
formerly  made  of  wood  or  natural  stone. 

Another  important  use  of  lime  is  in  the  preparation  of 
bleaching  powder.  This  article  is  consumed  in  enormous 
quantities  in  the  bleaching  of  cotton  and  linen  goods.  It 
has  also  been  employed  as  a  disinfecting  and  germicidal 
substance  in  sanitary  work  and  the  purification  of  water 
supplies  for  drinking  purposes. 

Calcium  hydroxide,  slaked  lime,  Ca(0H)2.  This  com- 
pound, when  pure,  is  a  light  white  powder.  It  is  slightly 
soluble  in  water,  forming  a  solution  called  limewater,  used 
as  a  mild  alkali  for  medicinal  purposes.  A  paste  of  the 
slaked  lime  in  water  is  sometimes  referred  to  as  milk  of  lime. 
Calcium  hydroxide  is  a  relatively  cheap  and  efficient  alkali 
and  is  used  in  many  industries  whenever  an  alkali  is  needed. 


A  FEW  IMPORTANT  METALB 


15: 


In  this  way  slaked  lime  is  used  in  the  preparation  of  am- 
monia, bleaching  powder,  and  potassium  hydroxide.  It 
is  also  used  to  purify  illuminating  gas,  to  remove  the  hair 
from  hides  in  the  tanneries,  and  for  making  mortar. 

Calcium  carbonate,  CaC03.  This  compound  is  found  in 
the  earth  in  a  number  of  valuable  mineral  forms.  Some  of 
these  are  not  markedly  crystalline,  while  others  do  occur  in 
quite  definite  shaped  crystals.  The  non-crystalline  or 
amorphous  includes  the  following  common  forms :  limestone 
(always  impure),  pearls,  chalk,  coral,  and  shells.  Of  these 
limestone  is  the  most  familiar  and  is  a  grayish  rock  usually 
found  in  hard  stratified  masses.  Whole  mountain  ranges 
are  sometimes  made  of  this  material.  Marl  is  a  mixture 
of  calcium  carbonate  and  clay.  The  other  forms  mentioned 
are  largely  calcium  carbonate. 

Crystalline  calcium  carbonate  occurs  in  the  following 
forms.     Iceland  spar  is  a  very  pure  and  transparent  form. 

Mexican  onyx  is 
a  massive  vari- 
ety, streaked  or 
banded  with  col- 
ors due  to  im- 
purities. Marble 
when  pure  is 
made  up  of  mi- 
nute calcite  crys- 
tals. Stalactites 
and  stalagmites 
are  icicle-like 
forms  found  in  caves.  Sometimes  calcium  carbonate  is 
found  in  needle  shaped  crystals,  which  are,  however, 
unstable  and  change  over  to  the  other  crystalline  variety. 
In  Figure  42  is  shown  a  specimen  of  an  interesting  form  of 
calcite,  the  bird's  nest  variety.  This  rock  is  made  up  of  a 
large  number  of  small  rounded  pebbles  of  calcium  carbon- 


Figure   42, — Bird's   nest   calcite. 


156  CHEMISTRY  OF  THE  FARM  AND  HOME 

ate  which  were  cemented  together  by  some  natural  cement, 
probably  acid  calcium  carbonate,  CaH2(C03)2.  In  the 
center  of  the  picture,  some  of  the  pebbles  have  been  separated 
from  each  other  and  replaced  without  the  cement. 

In ,  the  laboratory  calcium  carbonate  can  be  prepared 
by  the  reaction  of  a  soluble  calcium  salt  with  a  soluble 
carbonate.  The  product  is  a  soft  white  powder,  called 
precipitated  chalk,  and  is  used  as  a  polishing  powder,  whiting. 

Calcium  carbonate,  in  its  many  forms,  finds  a  host  of 
uses;  the  preparation  of  lime  and  carbon  dioxide,  in  blast 
furnace  operations,  in  the  manufacture  of  glass,  soda,  and 
crayon,  for  building  stones  and  for  correcting  soil  acidity. 

Hard  waters.  When  sulphates,  chlorides  and  carbonates 
of  calcium  and  magnesium  are  dissolved  in  water,  the  latter 
has  the  characteristic  commonly  designated  by  the  term 
hard.  Such  a  water  may  be  softened  by  boiling,  which 
removes  part  of  the  hardness,  and  by  adding  lye,  washing 
soda,  or  borax  which  combines  with  all  the  soluble  calcium 
and  magnesium  compounds  and  precipitates  them  from  the 
solution.  The  boiling  process  causes  any  calcium  or  mag- 
nesium acid  carbonate  in  the  solution  to  be  decomposed  and 
calcium  carbonate  to  be  precipitated.  The  hardness  caused 
by  such  material  is  called  temporary,  the  other  is  per- 
manent. 

CaH2(C03)2  -^  CaCOs  +  CO2  +  H2O. 
COPPER 

Introduction.  Copper  is  a  very  useful  metal.  It  has 
been  known  and  used  for  a  long  time  on  account  of  its  wide 
distribution  and  the  fact  that  it  occurs  in  the  free,  or  un- 
combined,  form.  It  is  comparatively  easy  to  produce  the 
metal  from  its  ores.  Copper  is  not  only  useful  in  the  free 
form,  but  it  is  an  essential  constituent  of  many  important 
alloys,  as  brass,  bronze,  etc.  Some  of  its  compounds  also 
have  industrial  uses,  and  certain  insecticides  and  fungicides 
contain  copper. 


A  FEW  IMPORTANT  METALS  l57 

Distribution.  Copper  occurs  in  nature  widely  distrib- 
uted and  in  a  large  number  of  compounds.  Some  of  the 
principal  ores  of  this  metal  are  free,  or  native  copper,  the 
oxides,  carbonates,  sulphide,  and  double  sulphides  of  iron 
and  copper.  The  United  States  produces  more  than  half 
the  world's  supply  of  copper.  The  principal  copper  ore 
sections  are  the  Lake  Superior  region,  the  Rocky  Mountain 
region,  and  the  southern,  or  Arizona  region.  Besides  the 
United  States,  the  greatest  producers  are  Spain,  Portugal, 
Chile,  Germany  and  Japan. 

Preparation.  Copper  is  easily  separated  from  its  ores 
by  one  of  a  number  of  methods:  by  heating  the  oxides  in 
a  current  of  hydrogen,  by  heating  the  oxides  with  carbon, 
by  precipitating  the  copper  with  a  cheaper  metal,  such  as 
iron  or  zinc,  and  by  electrolysis  of  a  copper  salt  solution. 
The  extraction  of  copper  from  its  ores  upon  a  large  scale 
depends  upon  the  character  of  the  ore.  The  processes  aim 
to  separate  the  copper  compound  from  other  impurities  and 
form  copper  oxide,  then  to  reduce  the  oxide  by  heating  with 
carbon,  and  finally  to  purify,  or  refine,  the  crude  product 
by  electrolysis.  The  separation  of  the  copper  from  impur- 
ities may  be  partly  mechanical,  such  as  washing  the  ore  to 
remove  earthy  or  rocky  impurities,  and  chemical,  such  as 
oxidizing,  or  roasting,  to  remove  the  sulphur  and  arsenic 
which  are  commonly  associated  with  the  copper. 

Physical  Properties.  Copper  is  a  rather  heavy  metal 
with  a  density  of  8.9.  It  has  a  characteristic  reddish  color, 
melts  at  1084°C.  and  is  rather  soft,  very  malleable,  ductile 
and  flexible,  but  tough  and  strong.  Its  ductihty  is  such 
that  it  may  be  drawn  out  into  fine  wire,  which  is  largely 
used  for  mechanical  purposes.  Its  toughness  enables  it 
to  be  beaten  out  into  thin  strong  sheets.  These  may  be  em- 
ployed in  making  copper  vessels  for  a  multitude  of  household 
and  industrial  purposes.  Another  characteristic  property  is 
its  power  to  conduct  heat  and  electricity,  in  which  respe 


i5§  CHEMISTRY  OF  THE  FARM  AND  HOMS 

it  is  next  to  silver.  Vast  quantities  of  copper  are  now  used 
for  electrical  purposes,  both  for  making  wire  and  apparatus. 
Copper  is  easily  precipitated  by  electrolysis.  Many  uses 
are  made  of  this  fact  in  the  arts,  for  example,  the  preparation 
of  electrotypes,  or  the  plates  used  in  printing  books,  depends 
upon  this  principle.  Copper  is  easily  precipitated  upon 
other  metals  in  a  compact  form  and  serves  to  protect  them. 

Chemical  Properties.  Copper  combines  with  a  great 
many  non-metals  and  forms  a  large  number  of  important 
compounds.  It  gives  two  series  of  compounds,  the  cuprous, 
and  the  cupric.  Copper  also  readily  unites  with  other 
metals  to  form  important  alloys.  Copper  and  zinc  produce 
brass;  copper,  zinc,  and  tin  produce  bronze;  copper  and  nickel 
give  German  silver;  and  copper  and  aluminium  give  alumin- 
ium bronze.  Many  other  alloys  of  copper  are  known,  all 
of  which  are  useful  for  certain  physical  or  chemical  prop- 
erties which  they  may  possess.  When  exposed  to  the  air 
copper  acquires  a  thin  skin  of  oxide  which  stops  further 
corrosion.  In  this  manner  the  chief  portion  of  the  metal 
is  protected  .  from  further  oxidation.  This  property  is 
radically  different  from  the  rusting  of  iron;  for  in  the  latter 
case  the  oxidation  progresses  under  the  surface,  so  that  event- 
ually the  entire  object  becomes  rusted.  When  copper  is 
heated  in  the  air  it  is  readily  oxidized  to  black  copper  oxide. 
When  exposed  to  moist  air  it  slowly  becomes  covered  with  a 
thin  layer  of  green  basic  carbonate,  verdigris.  Copper  is 
fairly  resistant  to  chemical  reagents,  being  practically  un- 
affected by  hydrochloric  acid,  dilute  sulphuric  acid,  and 
fused  alkalies.  Nitric  acid  and  hot  concentrated  sulphuric 
acid  do,  however,  dissolve  it. 

Cuprous  Compounds.  In  this  series  the  copper  is  univa- 
lent. Cuprous  compounds  are  not  as  common  as  the  other 
series,  since  they  are  easily  oxidized  into  the  latter. 

Cupric  Compounds.  In  this  series  the  copper  is  divalent. 
Cupric  salts  are  easily  made  by  dissolving  cupric  oxide  in 


A  FEW  IMPORTANT  METALS 


159 


acids  or  by  precipitation.     They  are  characterized  by  a  blue 
or  green  color  and  crystallize  well. 

Cupric  sulphate,  blue  vitriol,  bluestone,  CUSO4,  is  a  by- 
product of  a  number  of  processes  and  is  produced  in  large 
quantities.  It  forms  large  blue  crystals  which  lose  their 
water  of  crystalUzation  upon  heating  and  the  compound  then 


Figure  43. — Some  common  types  of  electrical  batteries,  including  the  Daniell 
cell,  the  sal  ammoniac  cell  and  the  dry  cell. 

becomes  a  white  powder.  The  compound  is  very  useful 
for  electrotyping,  in  making  electrical  batteries,  (See  different 
kinds  in  Figure  43)  and  fungicidal  preparations,  as  Bor- 
deaux mixture. 

MAGNESIUM 

Distribution.  Magnesium  is  a  very  abundant  element, 
occurring  as  the  carbonate,  sulphate,  chloride  and  siUcates. 
The  double  carbonate  of  magnesium  and  calcium  is  called 
dolomite;  magnesian  limestone  is  that  in  which  part  of  the 
calcium  carbonate  is  replaced  by  magnesium  carbonate. 
Talc  or  soapstone,  meerschaum,  and  asbestos  are  silicates  of 
magnesium. 

Preparation.  This  metal  is  prepared  by  the  electrolysis 
of  the  fused  double  chloride  of  magnesium  and  potassium. 


160  CHEMISTRY  OF  THE  FARM  AND  HOME 

Properties.  Magnesium  is  a  rather  tough  silvery  white 
metal  of  low  specific  gravity.  It  slowly  becomes  coated 
with  a  layer  of  the  carbonate.  It  is  less  active  than  calcium, 
but  decomposes  boiling  water  with  the  evolution  of  hydrogen. 
It  burns  in  the  air  with  a  dazzUng  white  light.  The  ash  of 
this  reaction  contains  both  the  oxide  and  the  nitride  of 
magnesium. 

Uses.  Powdered  magnesium  is  used  in  fireworks  and  in 
flash  light  powders  in  the  ratio  of  10  parts  of  magnesium  to 
17  parts  of  potassium  chlorate. 

Compounds.  Magnesium  oxide,  MgO,  is  prepared  by 
heating  the  carbonate  and  is  called  calcined  magnesia.  It 
is  a  white  powder  which  is  used  for  making  crucibles  and  for 
lining  electric  furnaces. 

Magnesium  sulphate,  Epsom  salts,  MgS04,  is  a  common 
substance  occuring  in  springs  and  salt  deposits.  It  is  used 
in  medicine,  the  textile  industry  and  some  chemical  works. 

Magnesium  carbonate,  MgCOa,  is  an  abundant  mineral. 
Its  double  salt  with  calcium  carbonate,  dolomite,  is  a  very 
common  rock,  composing  vast  mountain  ranges.  It  is  harder 
and  less  readily  attacked  by  acids  than  limestone,  and  is 
therefore,  useful  for  roadbeds  and  building  purposes. 

Magnesium  compounds  are  of  considerable  importance 
in  the  growth  of  plants.  The  element  seems  to  be  an  essen- 
tial constituent  of  chlorophyll  and  is  present  in  the  ash  of 
the  seed  to  a  greater  extent  than  calcium. 

ZINC 

Distribution.  Zinc  always  occurs  in  the  combined  form. 
It  is  not  widely  distributed,  being  found  in  small  areas. 
Its  ores  are  the  sulphide,  oxide,  carbonate  and  silicate  of 
zinc. 

Preparation.  The  ores  are  first  roasted  and  the  oxide 
thus  formed  reduced  by  means  of  coal  dust.  The  zinc  is 
volatile  and  may  be  distilled  and  collected. 


A  FEW  IMPORTANT  METALS  161 

Physical  Properties.  Zinc  is  a  bluish  white  metal  with 
a  high  luster.  Its  physical  properties  depend  upon  the  tem- 
perature and  previous  treatment  to  which  it  has  been  sub- 
jected. When  heated  to  a  low  temperature  it  is  malleable, 
but  becomes  brittle  at  higher  temperatures.  At  419°C.  it 
melts  and  with  further  heating  it  burns  with  a  very  bright 
blue  flame. 

Chemical  Properties.  The  exterior  surface  of  zinc 
metal  is  oxidized  by  moist  air,  but  further  oxidation  does 
not  take  place.  Zinc  does  not  affect  boiling  water  and 
when  quite  pure  is  barely  attacked  by  acids. 

Uses.  It  is  used  as  a  lining  for  water  vessels  and  for 
galvanizing  iron  to  protect  the  latter  from  rusting.  Zinc 
is  also  used  for  making  electrodes  for  the  various  types  of 
electrical  batteries.  (See  Figure  43.)  Another  important 
application  is  its  use  in  alloys,  examples  of  which  are  brass, 
an  alloy  of  zinc  and  copper,  the  different  bronzes,  coin 
metals  and  bearing  metals.  When  molten  metals  dissolve 
in  one  another  freely,  the  results  are  called  alloys.  When 
mercury  is  one  of  the  components,  the  name  amalgam  is 
applied  to  the  alloy. 

Compounds.  Zinc  oxide,  ZnO,  is  a  white  powder  and  its 
principal  use  is  as  a  white  pigment  in  paint,  when  it  is-called 
zinc  white.  It  is  not  affected  by  hydrogen  sulphide  and  is 
thus  superior  to  lead  paints  which  are  turned  black  by  that 
compound. 

Zinc  chloride,  ZnCl2,  is  often  used  to  impregnate  wood, 
as  fence  posts,  railroad  ties  and  telephone  poles,  and  protect 
them  against  rotting.  The  chloride  is  a  germicide  and  pre- 
vents decay. 

IRON 

Introduction.     Iron  is  undoubtedly  the  most  useful  of 
metals.     It  is  also  one  of  the  most  widely  distributed.     It 
is  an  essential  constituent  of  plants  and  of  the  coloring  matter 
of  blood. 
11— 


162 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Distribution.  This  metal  occurs  as  oxides,  carbonates, 
and  sulphides  in  widely  distributed  ores.  It  is  also  found  in 
the  soil  and  in  natural  waters. 

Preparation.  Iron  ores  are  reduced  by  heating  them 
with  coke  or  charcoal  in  a  blast  furnace.  (Figure  44.)  Such 
a  furnace  may  vary  in  height  from  30  to  90  feet  and  be  con- 
structed of  firebrick  reinforced  with  iron.     Besides  the  charge 

of  iron  ore  and  coke  or  charcoal, 
limestone  is  also  added.  These 
materials  are  placed  in  the  fur- 
nace in  successive  layers.  When 
the  furnace  is  fired  a  blast  of  hot 
air  is  forced  in  through  the  pipes  at 
the  bottom  to  increase  the  intens- 
ity of  the  reaction.  The  oxygen  of 
the  air  unites  with  the  carbon  of 
the  fuel  in  the  lower  part  of  the 
furnace  and  forms  carbon  dioxide, 
CO 2-  This  is  reduced  by  the  hot 
carbon  further  up  in  the  furnace 
to  carbon  monoxide,  CO.  The 
latter  gas  combines  with  the  oxy- 
gen of  the  iron  oxide  and  iron  and 
carbon  dioxide  result. 
Fe304  +  4  CO  ->  3  Fe  +  4  CO2 
The  iron  is  drawn  off  through 
tap  holes  in  the  extreme  bottom  of 
the  furnace  and  is  run  into  molds, 
forming  the  bars  called  pigs,  or  it  is 
transferred  to  the  converters  and 
made  into  steel.  In  order  to  remove  the  earthy  impurities 
of  the  ore  and  the  ash  of  the  fuel,  limestone  is  added  as  a 
flux.  The  limestone  combines  with  such  waste  material 
and  forms  the  glassy  slag  which  is  run  off  a  little  above 
the  iron. 


Figure  44. — A  blast  furnace. 


A  FEW  IMPORTANT  METALS  163 

Kinds  of  Iron.  There  are  various  grades  of  iron  which 
differ  from  one  another  principally  in  the  amounts  of  certain 
impurities  which  they  may  contain.  These  impurities  are 
carbon,  phosphorus,  sulphur  and  silicon.  The  difference 
in  the  amount  of  carbon  serves  as  a  basis  for  the  general 
classification  of  iron  into  the  following  three  grades,  cast  iron, 
wrought  iron  and  steel.  Cast  iron  has  from  1.5%  to  7% 
carbon.  It  melts  at  low  temperatures  and  is  too  brittle  to 
be  welded  or  forged.  Wrought  iron  contains  less  carbon  than 
either  of  the  other  two  kinds,  0.6%  or  less.  It  is  tough  and 
malleable  and  requires  a  high  temperature  to  melt  it.  It 
can  be  welded  and  forged,  but  not  cast  or  tempered. 

Steel  contains  more  carbon  than  wrought  iron,  but  less 
than  cast  iron.  Its  melting  point  is  between  the  other  two 
and  it  can  be  forged,  welded,  cast  and  tempered.  Steel  is 
manufactured  either  by  adding  carbon  to  wrought  iron 
or  heating  cast  iron  and  wrought  iron  together  in  a  Bessemer 
converter  or  open  hearth  furnace.  The  converter  is  a  large 
pear  shaped  furnace  so  arranged  that  blasts  of  air  can  be 
forced  up  through  the  mass.  The  air  oxidizes  the  silicon 
and  carbon  in  the  steel  and  reduces  their  amount.  In  the 
open  hearth  furnace,  pig  iron  is  mixed  with  wrought  iron  and 
heated  on  a  hearth  with  an  oxidizing  gas  flame.  The  same 
result  is  achieved  as  in  the  converter. 

Properties.  Pure  iron  is  not  common.  Wrought 
iron  is  the  purest  form  in  commerce.  Wrought  iron  is  ductile 
and  a  fairly  good  conductor.  Steel  is  a  very  hard  form  of 
iron.  Iron  decomposes  steam  at  a  high  te^nperature.  It 
also  rusts  in  moist  air  and  carbon  dioxide.""  Iron  reacts 
readily  with  dilute  acids.  It  forms  two  classes  of  compounds, 
ferrous  and  ferric. 

Uses.  Iron  in  its  different  grades  is  of  fundamental 
importance  in  the  progress  of  civilization.  For  the  build- 
ing of  bridges  and  railroads,  for  the  erection  of  factories  and 
office  buildings,  for  the  manufacture  of  engines  and  mach- 


164  CHEMISTRY  OF  THE  FARM  AXD  HOME 

inery,  iron  has  been  the  metal  which  has  served  man  most 
in  his  various  activities.  This  is  partly  on  account  of  its 
great  abundance,  which  makes  it  a  cheap  and  readily  acces- 
sible metal,  and  partly  on  account  of  its  physical  and  chemical 
properties.  Though  iron  is  of  the  greatest  importance  and 
usefulness  in  the  metallic  form,  some  of  its  compounds  are 
of  value  commercially  and  for  plant  and  animal  life. 

ALUMINIUM 

Introduction.  About  three  fourths  of  the  earth's  surface 
is  composed  of  silicon  and  oxygen  and  one  third  of  the  re- 
mainder is  aluminium.  These  three  elements  have  a  great 
attraction  for  one  another  and  are  found  in  the  form  of  sili- 
cates. On  account  of  the  great  affinity  of  aluminium  for 
oxygen  and  silicon,  aluminium  was  not  isolated  in  the  pure 
elementary  form  until   1828. 

Occurrence.  Aluminium  does  not  occur  free,  but  is  the 
most  abundant  and  widely  distributed  metal  in  nature. 
Some  of  the  most  important  minerals  and  rocks  contain  this 
element.  Feldspar  and  mica  are  silicates  of  aluminium; 
granite  is  a  mixture  of  quartz,  feldspar,  and  mica;  clay  is  a 
decomposition  product  of  granite  and  similar  rocks  or  min- 
erals containing  silicon  and  aluminium. 

Preparation.  Aluminium  is  manufactured  by  an  elec- 
trolytic process  somewhat  as  follows:  The  furnace  consists 
of  a  box  of  iron  lined  with  a  mixture  of  coke  and  tar.  This 
forms  the  negative  electrode  while  the  positive  electrode 
consists  of  large  carbons  suspended  by  copper  rods.  A 
charge  of  cryolite,  a  double  fluoride  of  aluminium  and  so- 
dium, is  used  to  start  the  furnace  after  which  pure,  dry, 
alumina  is  added.  The  process  is  continuous  as  the  cryolite 
bath  remains  unchanged.  The  aluminium  collects  at  the 
bottom  of  the  furnace  and  is  drawn  off  at  frequent  intervals. 
The  oxygen  unites  with  the  carbon  and  forms  carbon  monox- 
ide which  escapes. 


A   FEW  IMPORTANT  METALS  165 

Properties.  Aluminium  is  a  white  lustrous  metal  of  low 
specific  gravity  (2.6),  whereas  the  other  common  metals 
are  from  seven  to  nine  times  as  heavy  as  water.  It  melts  at 
about  660°C.  and  vaporizes  at  the  temperature  of  the  electric 
furnace.  It  is  a  good  conductor,  is  ductile  and  malleable, 
and  is  capable  of  receiving  a  very  high  polish.  At  white 
heat,  aluminium  burns  to  aluminium  oxide,  AI2O3.  Hydro- 
chloric acid  reacts  with  it,  but  nitric  acid  and  dilute  sulphuric 
acid  do  not  ordinarily  affect  the  metal.  It  reacts  with  salt 
solutions,  if  a  little  free  acid  is  present.  It  is  also  soluble 
in  the  alkalies,  sodium  and  potassium  hydroxides,  forming 
the  aluminates  of  these  metals  and  free  hydrogen.  Alu- 
minium combines  directly  with  the  halogens  and  with  carbon, 
silicon,  nitrogen  and  some  other  elements.  It  does  not  tarn- 
ish in  the  air  or  when  exposed  to  vapors  containing  sulphur. 

Compounds.  Aluminium  oxide,  alumina,  AI2O3.  This 
substance  occurs  in  the  form  of  the  ruby,  sapphire,  and 
corundum.  Emery  is  an  impure  form  of  corundum  and  is 
used   for   grinding   and   polishing. 

Aluminium  hydroxide,  A1(0H)3,  is  found  as  a  natural 
substance,  bauxite.  This  compound  reacts  with  both  acids 
and  alkaUes  except  ammonium  hydroxide.  The  hydroxide 
is  used  as  a  mordant  in  the  dyemg  industry,  that  is,  to  fix 
the  dye  in  fabrics  which  do  not  readily  hold  color. 

Alums  are  double  salts  of  aluminium  sulphate  with 
sulphates  of  univalent  metals  as  potassium  sulphate. 
Alums  crystallize  with  24  molecules  of  water  of  crystal- 
lization. Other  trivalent  metals  may  replace  the  aluminium 
in  so  called  alums. 

Uses.  Aluminium  is  used  in  the  manufacture  of  iron 
and  steel  to  remove  any  oxygen  the  iron  may  have  in  combi- 
nation and  thereby  increases  the  fluidity  of  cast  iron  and  steel. 
It  is  also  used  as  a  conductor  of  electricity,  in  the  manufac- 
ture of  alloys,  kitchen  utensils  and  scientific  instruments. 
Aluminium  powder  is  used  for  flash  lights  and  to  reduce  the 


166      CHEMISTRY  OF  THE  FARM  AND  HOME 

oxides  of  many  metals  which  cannot  be  reduced  by  carbon. 
A  mixture  of  aluminium  with  various  metallic  oxides  comes 
ready  prepared  under  the  name  of  thermite.  When  the 
mixture  is  ignited,  the  aluminium  unites  with  the  oxygen 
of  the  metallic  oxide  and  liberates  the  metal.  Much  heat  is 
liberated  in  the  reaction  and  the  process  is  used  in  weld- 
ing operations  where  a  large  amount  of  local  heat  is 
required.  In  alloys  the  aluminium  greatly  increases  the 
tensile  strength  of  the  metals  with  which  it  is  combined. 

Porcelain,  stoneware,  etc.,  are  made  from  aluminium 
silicate,  in  the  pure  form  called  kaolin,  in  the  impure  form, 
clay.  Porcelain  is  made  by  mixing  kaolin  with  feldspar, 
shaping  the  mixture  into  the  desired  form  and  heating  it  to 
a  high  temperature.  The  more  fusible  feldspar  melts  and 
cements  the  whole  together.  Porcelain  is  hard  and  trans- 
lucent and  withstands  the  action  of  heat  and  chemicals 
better  than  glass.  Stoneware  is  opaque,  not  having  been 
heated  as  much  as  in  the  case  of  porcelain.  Earthenware 
is  made  from  common  clay,  hardened  by  heat  but  not  fused. 
It  is  glazed  by  the  addition  of  some  common  salt  to  the  fur- 
nace at  the  time  of  heating.  This  vaporizes  at  the  high 
temperature  of  the  furnace  and  combines  with  the  clay  form- 
ing a  covering  of  sodium  aluminium  silicate  over  the  surface. 

SUMMARY 

The  alkali  metals  constitute  a  group  of  elements  which  are  some- 
what similar  in  their  properties.  Sodium  and  potassium  are  the  im- 
portant members  of  the  group  to  be  considered  here.  They  are  very 
active,  hence  always  occur  in  combination.  These  compounds  are 
important  for  household,  industrial,  and  agricultural  purposes.  Com- 
mon salt,  washing  soda,  baking  soda  and  ordinary  lye  are  examples  of 
some  common  compounds  of  sodium.  The  compounds  of  potassium 
are  of  especial  importance  for  use  in  agriculture  as  fertilizers. 

Calcium  occurs  abundantly,  but  always  in  the  combined  form. 
Its  compounds  are  found  in  the  earth's  surface  and  in  plant  and  animal 
life.  Calcium  compounds  are  of  great  value  to  man  since  they  are  used 
in  erecting  buildings,  in  the  chemical  industries  and  in  agriculture. 

Copper  is  one  of  the  oldest  known  metals.     This  is  because  it  oc- 


A  FEW  IMPORTANT  METAL 8  167 

curs  in  the  free  as  well  as  the  combined  form.  The  refining  of  copper 
is  an  important  operation  on  account  of  the  vast  commercial  use  of 
the  element.  It  has  properties  which  make  it  especially  valuable  for 
electrical  work.  It  is  also  a  constituent  of  many  important  alloys. 
Some  of  its  compounds  are  useful,  the  chief  one  probably  being  copper 
sulphate. 

Magnesium  is  a  very  abundant  element  and  its  compounds  are 
important  for  commercial  purposes  and  in  plant  growth. 

Aluminium  is  the  most  abundant  metal.  Many  natural  minerals 
contain  the  element  and  its  importance  can  be  realized  from  the  facts 
that  its  compounds  form  the  bulk  of  the  soil  and  are  the  chief  material 
used  in  the  manufacture  of  porcelain  and  stoneware.  The  metal 
itself  has  increasing  commercial  usefulness. 

While  zinc  is  not  widely  distributed,  it  and  its  compounds  are  of 
great  value  for  the  purpose  of  preventing  the  rusting  of  iron  and  the 
rotting  of  wood. 

Iron  is  found  practically  everywhere.  It  is  undoubtedly  the 
most  important  metal  from  a  commercial  standpoint  as  it  is  used 
so  largely  for  engineering  and  structural  purposes. 

QUESTIONS 

1.  State  one  important  commercial  use  of  each  metal  studied. 

2.  Name  differences  in  the  properties  of  sodium  and  potassium. 

3.  What  substances  studied  are  prepared  from  common  salt? 

4.  What  is  the  difference  between  washing  soda  and  baking  soda? 

5.  Why  is  the  element  calcium  of  importance  to  mankind? 

6.  State  the  cause  of  hard  waters  and  means  of  softening  them. 

7.  Compare  the  hardening  of  mortar  with  the  setting  of  cement 
and  plaster  of  Paris. 

8.  Why  do  caves  often  occur  in  limestone? 

9.  Give  the  chemical  names  and  state  the  uses  of  the  following: 
lye,  common  salt,  saleratus,  washing  soda,  wood  ashes,  Chile  salt- 
petre and  gypsum. 

10.  What  is  the  difference  between  quartz  and  hmestone;  be- 
tween gypsum  and  limestone? 

11.  Why  is  aluminum  of  unusual  interest  in  connection  with 
the  study  of  the  earth's  surface? 

12.  Mention  some  important  uses  of  aluminium. 

13.  Why  is  it  necessary  to  produce  a  slag  in  the  working  of  a 
blast  furnace? 

14.  How  may  iron  be  protected  against  corrosion? 

15.  What  is  meant  by  the  following  expressions:  electro-plating, 
slag,  alloy? 

16.  Compare  the  properties  of  the  metals  studied. 

17.  What  metals  are  prepared  by  electrolytic  methods? 

18.  What  commercial  uses  are  made  of  sodium  nitrate,  sodium 
chloride  and  calcium  carbonate? 

19.  Make  a  table  showing  the  principal  properties  of  at  least 
five  elements  which  are  solids  at  ordinary  temperatures. 

20.  Name  as  many  chemicals  as  possible  (which  you  have  studied) 
that  are  usuaMy  found  in  the  ordinary  household. 


CHAPTER  VI 
THE  PLANT  AND  ITS  PRODUCTS 

Importance  of  the  Plant.  In  preceding  chapters  we  have 
learned  about  several  important  chemical  elements  and 
some  reactions  in  which  they  take  part.  We  are  now 
occupied  with  the  study  of  chemical  properties  and  reactions 
of  some  materials  very  important  in  agriculture  and  daily  life. 
None  of  these  materials  are  more  important  than  those  pro- 
duced by  the  living  plant.  Let  us  consider  the  reasons  for 
the  great  importance  of  plants  in  agriculture.  Have  you 
ever  assembled  in  your  mind  the  sources  of  the  various 
feeding  stuffs  of  animals?  It  will  be  well  to  draw  up  as 
long  a  list  of  them  as  you  can,  remembering  that  man  is 
included  with  the  animals.  You  are  acquainted,  of  course, 
with  the  uses  of  cotton,  linen,  flax  and  hemp  fibers.  Do 
you  know  their  sources?  Recall  for  a  moment  the  sources 
of  the  various  kinds  of  wood  used  in  the  manufacture  of 
tools  and  furniture  and  in  the  erection  of  buildings.  Can 
you  not  suggest  many  other  ways  in  which  plants  are  of 
service  to  man? 

In  some  types  of  farming  the  plant  itself  is  the  chief 
product.  This  is  true  when  the  business  is  limited  to  the 
raising  of  grain  or  truck  crops,  such  as  wheat  or  onions.  In 
live  stock,  dairy  or  general  farming,  however,  the  plant  is 
rather  a  stepping  stone  to  the  chief  product.  In  the  form 
of  various  feeding  stuffs  it  serves  as  a  channel  through 
which  simple  compounds  of  the  air  and  the  soil  are  converted 
into  the  complex  compounds  of  meat,  milk  and  other  animal 
products.  Let  us  try  to  see  this  relation  more  clearly  as  we 
proceed  with  our  study. 

168 


THE  PLANT  AND  ITS  PRODUCTS  169 

Composition  of  the  Plant.  Before  the  processes  of 
growth  can  be  profitably  studied  it  is  necessary  to  become 
familiar  with  the  composition  of  the  plant.  For  this  rea- 
son we  will  now  consider  the  composition  of  the  nearly 
mature  corn  plant,  with  ears  glazed  and  ready  for  shocking. 
Table  V.  gives  the  average  amounts  of  the  most  important 
organic  compounds  and  of  the  chemical  elements  in  1,000 
pounds  of  the  plant. 


Table  V.- 

—Important  Elements  and  Organic  Compounds  of  the  Corn 
Plant 

Pounds  per  1,000  pounds  of  plant 

Water... 

790 

Dry  matter  210 


fProtein 18 

Organic  matter  198  j  Fat 5 

I  Carbohydrates . .  175 

198 

Ash 12 


210 


Hydrogen 


/in  water 88 

\in  organic  matter 13 


1,000 


Oxygen|jJ 


101.0 


m  water 705 

in  organic  matter 89 

794.0 

Carbon 91.0 

Nitrogen 3.0 

Phosphorus 0.5 

Sulphur 0.1 

Calcium 1.2 

Magnesium 0.8 

Potassium 3.2 

Sodium 0.3 

Iron  0.2 

Chlorine 0.4 

Silicon  1.1 

Other  elements 3.2 


1,000.0 


The  water  of  Table  V.  is  the  amount  lost  by  drying  the 
plant  at  100°C.  Do  you  see  any  good  reason  for  the  use 
of  this  particular  temperature?     The  loss  includes  water 


170 


CHEMISTRY  OF  THE  FARM  AND  HOME 


existing  in  the  free  state  in  the  fresh  tissues  of  the  plant. 
It  also  includes  water  combined  with  other  compounds  in 
the  plant,  after  the  manner  of  the  water  of  crystallization 
of  certain  salts. 

The  dry  matter  is  the  residue  left  after  drying  at  100°C. 
It  consists  of  a  mixture  of  organic  and  inorganic  compounds 
containing  the  elements  Hsted  in  the  table.     The  ash,  or 

ashes,  is  separated  from  the  or- 
ganic matter  by  a  simple  method 
which  you  will  readily  suggest. 
Care  must  be  taken,  however,  to 
avoid  volatilizing  some  of  the 
ash  constituents.  A  clear-cut  dis- 
tinction between  elements  that 
exist  in  organic  compounds  and 
those  existing  only  in  inorganic 
form  is  impossible.  They  may 
all,  at  some  stage  or  other,  be 
present  in  the  plant  in  organic 
forms.  From  such  compounds, 
as  well  as  from  the  inorganic 
compounds,  they  would  become 
ash  constituents  by  burning. 

The  organic  compounds  of 
the  plant  will  be  so  important 
in  our  succeeding  study  of 
growth,  that  we  must  classify  and  study  them  at  this 
point.  The  carbohydrates  form  the  ground  work  both  of 
the  processes  and  of  the  products  of  plant  growth.  They 
contain  carbon,  hydrogen  and  oxygen.  The  last  two 
elements  are  generally  present  in  the  proportion  of 
two  atoms  to  one,  respectively.  They  occur  in  the 
same  proportion  in  a  very  important  and  abundant  com- 
pound. What  is  the  compound?  Do  you  not  see  the 
derivation    of   the   term   carbohydrate?     The  chief  carbo- 


Figure  45.  Jean  Boussingault, 
1802-1887.  This  French  chem- 
ist discovered  that  plants  can- 
not take  the  nitrogen  they  need 
directly  from  the  air.  He  also 
made  some  of  the  earliest  chem- 
ical studies  of  the  processes  of 
growth  in  plants. 


THE  PLANT  AND  ITS  PRODUCTS  171 

hydrates  of  the  plants  can  be  classified  from  the  simple 
to  the  complex  as  follows: 

Group  1 — 

Monosaccharides{p-tj-...-. .••■•.. ••■•■^^ 
Group  2 — 

Disaccharides{M^>r  .v.;;: .::;:::::::::::::  .^llill^lf''' 

Group  3—  f 

Polysaccharides{|'-»>„^-  ■::;:;:::;;::;:;•:;; (CeHjoO.), 

The  compounds  of  the  first  group  are  called  hexoses, 
from  the  number  of  carbon  atoms  they  contain.  They  are 
also  called  monosaccharides  because  they  are  the  simplest 
or  unit  compounds  in  the  series.  What  difference  do  you 
observe  between  the  two  compounds  in  the  second  group? 
The  term  saccharide  is  derived  from  the  Greek  word  for 
sugar.     Do  you  see  the  significance  of  these  prefixes? 

Dextrose  is  common  in  small  amounts  in  leaves,  germi- 
nating seeds,  flowers  and  fruits.  On  account  of  its  great 
usefulness  in  the  plant  it  never  accumulates  in  large  quanti- 
ties. It  is  either  burned  as  a  source  of  energy  or  converted 
to  some  of  the  higher  carbohydrates. 

Levulose  differs  from  dextrose  in  the  structure  of  its 
molecule.  Along  with  this  difference  go  differences  in 
chemical  and  physical  properties.  It  occurs  only  in  small 
amounts  in  some  fruits. 

Maltose  occurs  in  small  amounts  in  leaves,  but  espe- 
cially in  germinating  seeds,  where  it  is  produced  from  starch. 
On  boiling  with  dilute  acids  or  by  the  action  of  the  enzyme 
maltase  it  is  converted  into  two  molecules  of  dextrose. 
The  nature  of  enzymes  will  be  described  when  the  chemis- 
try of  growth  is  discussed. 

Sucrose  occurs  in  large  amounts  in  some  plants,  as  in  the 
stalk  of  sugar  cane  and  the  root  of  the  sugar  beet.  It  also 
occurs  in  many  seeds  in  small  amounts,  and  in  leaves. 
In  these  cases,  it  is  a  reserve  food  of  the  plant.     It  is  rapidly 


172 


CHEMISTRY  OF  THE  FARM  AND  HOME 


converted  to  starch  in  the  ripening  seed  of  corn,  while  in 
the  sugar  beet  it  is  used  directly  for  seed  production  in  the 
second  year  of  growth.  By  boiling  with  dilute  acids  or  by 
the  action  of  the  enzyme  invertase,  this  sugar  is  converted 
into  one  part  each  of  dextrose  and  of  levulose.  The  latter 
action  occurs  in  the  plant  whenever  sucrose  is  used. 

Starch  occurs  in  small  amounts  in  leaves,  but  is  especially 


^ 

Q    0 

^°o 

.3         ■ 

^ 

^c, 

0    /i 

■  9 

0 

0^^ 

J.   , 

■  ^     ^'^  , 

0 

.-  'A 

/          ) 

'•^ 

....~- 

\     ' 

-O 

'    Q 
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J 

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i 

4^ 

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HlF 

^Ir 

OJ    ...i 

Figure  46,     The   appearance    of    granules  of  different  starches  under  the  micro- 
scope.   Corn  starch  on  the  left,   potato  starch  on  the  right. 

abundant  in  the  other  organs,  where  it  is  a  reserve  food.  It 
is  most  commonly  found  in  seeds.  Each  kind  of  plant  pro- 
duces starch  in  the  form  of  granules  which  are  characteristic 
in  size,  shape,  and  markings.  Some  of  these  differences,  as 
illustrated  in  Figure  46,  make  it  possible  to  determine  the 
source  of  foods  by  the  aid  of  the  microscope. 

Starch  is  not  soluble  in  water,  but  by  treatment  with 
boiling  water  it  forms  soluble  starch  paste.  This  paste  is 
converted  to  dextrose  by  boiling  with  dilute  acids.  The 
enzyme  diastase  converts  it  to  maltose.  In  the  formula 
for  starch,  the  x  following  the  brackets  denotes  that  the 
molecule  contains  an  unknown  multiple  of  the  unit  struc- 
ture within  the  brackets.  What  difference  do  you  observe 
between  this  unit  and  the  formula  of  dextrose?  The  pre- 
ceding  classification   indicates   only   a   probable   difference 


THE  PLANT  AND  ITS  PRODUCTS  173 

in  the  value  of  x  between  starch  and  cellulose.  Since 
cellulose  cannot  be  converted  to  dextrose  by  boiling  with 
dilute  acids,  however,  we  know  its  molecular  structure 
differs  from  that  of  starch.  This  carbohydrate  dissolves 
in  strong  acids,  and,  on  boiling  the  diluted  solution,  dex- 
trose and  other  sugars  are  produced.  The  enzyme  cellulase 
converts  it  to  soluble  compounds.  These  differences  show 
that  the  simpler  carbohydrate  units  are  modified  differ- 
ently in  producing  starch  on  the  one  hand,  and  cellulose 
on  the  other.  The  result  is  a  more  stable  and  resistant 
compound  in  the  case  of  cellulose.  This  fits  it  for  its  uses 
of  support  and  protection  to  the  plant.  Cellulose  rarely 
occurs  pure,  although  cotton  fiber  is  pure  cellulose.  It 
is  usually  associated  with  other  related  compounds. 

Have  you  noticed  that,  so  far,  we  have  described  only 
ways  for  producing  the  simpler  from  the  more  complex 
carbohydrates?  It  is  not  yet  possible  to  proceed  in  the 
opposite  direction  in  the  laboratry.  Compare  the  formulae 
of  the  classification  carefully  and  see  if  you  can  detect 
what  general  change  occurs  in  passing  in  the  one  or  the 
other  direction.  This  change  emphasizes  the  importance 
of  a  very  common  compound  in  the  life  of  the  plant. 
What  is  it? 

Fats  contain  the  same  chemical  elements  as  the  car- 
bohydrates. They  are  quite  different  from  the  latter, 
however,  in  chemical  structure.  These  compounds  are 
formed  by  the  union  of  certain  organic  acids,  the  fatty  acids, 
with  the  organic  base  glycerol,  or  glycerine.  This  base 
has  three  hydroxyl  or  basic  radicles.  The  following  equa- 
tion expresses  the  formation  of  the  fat  acetin  from  acetic 
acid,  the  acid  to  which  vinegar  owes  its  sourness: 
C3H5(OH)3  +  3CH3COO  H->C3H5(CH3COO)3  +  3H2O 
Glycerol     +  Acetic  acid      ->  Acetin  +  Water 

In  the  preceding  equation  the  acid  hydrogens  and  the 
basic  hydroxyls  combine  to  form  water.     If  we  substitute 


174  CHEMISTRY  OF  THE  FARM  AND  HOME 

NaOH  and  HCl  for  the  base  and  acid  respectively  in  the 
equation,  what  product  shall  we  have  besides  water?  Can 
you  now  suggest  a  nam©  for  the  chemical  structure  of  fats? 
The  old-fashioned  home  process  of  soap-making  involved 
the  boiling  of  waste  fats  with  the  leachings  from  wood  ashes. 
In  this  process  potassium  of  the  potassium  carbonate  in 
the  ashes  replaces  the  glycerol  of  the  fat. 

Fats  are  present  in  plants  mostly  as  reserves  in  the  seed. 
They  exist  chiefly  in  the  liquid  state  called  oil.  Castor 
oil  forms  about  one  half  of  the  castor  bean.  Many  other 
seeds  contain  so  much  oil  as  to  be  greasy  to  the  touch. 
Name  some.  Recall  the  method  by  which  the  housewife 
"dry  cleans"  grease  spots  from  clothing.  Could  it  be  used 
to  remove  the  oil  from  seeds?  As  a  means  to  appreciating 
the  economy  of  fats  as  sources  of  energy  for  germination, 
calculate  the  percentages  of  carbon  in  starch  and  in  olein. 
Olein,  the  chief  fat  of  castor  oil,  has  the  formula  C57H104O6. 
Which  compound  will  produce  the  more  heat  when  burned? 
The  oil  of  any  plant  is  a  mixture  of  several  fats.  These 
compounds  are  produced  in  the  ripening  seed  from  sugars 
of  the  plant  sap.  During  germination  they  are  cleaved 
by  the  enzyme  lipase  to  glycerol  and  free  fatty  acids. 

The  proteins  are  very  complex  compounds.  Besides 
the  elements  which  occur  in  carbohydrates  and  fats,  they 
contain  nitrogen  and  sulphur.  The  kind  called  nucleo- 
proteins,  on  account  of  their  abundance  in  the  nuclei  of  cells, 
contain  phosphorus  also.  Proteins  are  most  abundant  in 
seeds,  where,  like  the  other  compounds,  they  serve  as  food 
for  the  seedling.  They  are  also  necessary  constituents 
of  all  living  cells.  By  hot,  strong  acids  and  by  the  enzymes 
called  proteases  they  are  converted  to  simpler  compounds. 
These  products  are  the  amino  acids  and  amides.  The  former 
are  related  to  both  ammonia  and  the  fatty  acids  and  are 
weak  acids.  The  latter  are  relatives  of  both  ammonia 
and  amino  acids.     They  are  neutral  salt-like  compounds. 


THE  PLANT  AND  ITS  PRODUCTS  175 

Only  small  amounts  of  water-soluble  proteins  occur  in  the 
plant.  Where  these  compounds  are  to  be  carried  about, 
they  are  converted  to  amino  acids  and  amides,  or  interme- 
diate compounds,  which  dissolve  in  the  sap.  Some  seeds 
contain  four  or  five  per  cent  of  proteins  soluble  in  strong 
alcohol.  These  compounds  include  zein  of  corn  and  gliadin 
of  wheat.  The  latter  is  a  constituent  of  the  gluten  to 
which  the  bread  dough  owes  its  important  properties. 
By  far  the  largest  proportion  of  plant  proteins  are  those 
soluble  in  weak  salt  solutions.  They  are  called  globulins. 
One  of  them,  conglutin,  forms  about  one  fourth  of  the  lupine 
seed.  Of  all  the  compounds  of  plants  the  proteins  are 
most  closely  connected  with  the  chemical  processes  of  life. 
By  the  action  of  acids  and  enzymes,  nearly  twenty  differ- 
ent amino  acids  and  amides  have  been  obtained  from  them. 
Some  of  these  products  are  very  complex  structures.  Thus, 
so  far  as  complexity  of  the  molecule  is  required,  proteins 
are  well  suited  to  the  varied  chemical  reactions  which  occur 
in  life  processes. 

Of  the  many  compounds  found  in  plants  but  not  in- 
cluded in  Table  V,  we  can  take  notice  of  but  a  few.  The 
alkaloids,  especially  important  in  medicine,  include  quinine 
of  a  certain  bark,  morphine  of  the  poppy,  and  nicotine  of 
tobacco.  They  are  bases  of  the  same  general  structure  as 
ammonia.  Waxes,  which  form  the  bloom  of  certain  leaves 
and  fruits,  are  close  relatives  of  the  fats.  They  contain 
some  other  base  than  glycerol  and  only  one  fatty  acid  mole- 
cule in  their  structure.  Terpenes  are  the  chief  constituents 
of  pitches,  turpentine,  and  rubber.  A  dictionary  will  help 
you  to  learn  the  source  and  uses  of  these  substances.  The 
aroma  of  many  plants,  such  as  the  spice  carnation,  is  due 
to  terpenes  and  related  compounds.  The  terpenes  contain 
only  carbon  and  hydrogen.  Organic  acids  and  their  salts 
cause  the  sourness  of  many  fruits  and  some  leaves,  as  in 
the  currant  and  rhubarb  plants. 


176  CHEMISTRY  OF  THE  FARM  AND  HOME 

The  ash,  or  ashes,  of  plants  contains  many  compounds. 
The  proportion  of  these  varies  with  the  kind  of  plant  and 
the  composition  of  the  soil.  All  inorganic  elements  present 
in  the  soil  are  likely  to  be  found  in  the  plant  ash,  but,  for 
reasons  we  shall  learn  later,  they  are  not  likely  to  be  found 
in  the  same  proportions  in  which  they  exist  in  the  soil. 
The  most  abundant  of  the  ash  compounds  are  silica,  pof-assitim 
carbonate,  calcium  sulphate,  and  calcium  phosphate.  Silica 
exists  in  the  plant  in  the  free  form  and,  as  an  inorganic  or 
non-burnable  constituent,  is  left  in  the  ash.  Calcium  sul- 
phate can  be  derived  entirely  from  organic  compounds,  the 
calcium  being  contributed  by  calcium  salts  of  organic  acids 
and  the  sulphur  by  proteins.  One  can  see,  therefore,  that 
the  ash  is  not  the  inorganic  matter  of  the  plant. 

Having  surveyed  the  compounds  of  the  plant,  let  us 
study  the  process  by  which  they  are  formed. 

The  growth  of  the  plant  is  the  result  of  many  chemical 
and  physical  changes.  The  nature  of  some  of  these  changes 
is  not  well  known. 

You  must  have  observed  that  some  plants  which  grow 
upon  decayed  wood  or  leaves  in  shaded  spots  are  nearly 
colorless.  What  is  the  most  common  plant  color  with  which 
you  are  familiar?  With  this  difference  of  color  is  associated 
a  great  difference  of  methods  by  which  plants  obtain  their 
food.  The  green  plants  manufacture  their  food  from  carbon 
dioxide  obtained  from  the  air  and  water  and  salts  obtained 
from  the  soil.  Other  plants  obtain  their  food  from  either 
dead  or  living  tissues  of  the  higher  green  plants.  The 
destructive  rusts  and  smuts  of  grains  are  plants  of  the  latter 
kind.     Can  you  suggest  others? 

Chief  among  the  processes  of  growth  of  the  higher  plants 
are  the  absorption  of  food  materials,  the  formation  and 
usage  of  foods,  and  the  excretion  of  waste  products.  All 
of  these  processes  occur  simultaneously  within  the  limits  of 
units  of  the  plant  called  cells.     Some  of  the  smallest  forms 


THE  PLANT  AND  ITS  PRODUCTS 


177 


WAU 

PRoro 

PLASM 


NUCLEUS 


of  green  plants,  such  as  the  algae  which  form  sUmy  films  on 
damp  rocks,  consist  of  a  single  cell  each.  In  most  cases, 
however,  multitudes  of  cells  are  united  to  form  tissues,  such 
as  wood  and  bark.  These  tissues  are,  in  turn,  related  to 
form  organs,  such  as  the  leaf  and  root.  The  burden  of  the 
processes  of  growth  is  distributed  among  these  organs.  A 
good  example  of  the  physical  changes  of  growth  is  the  move- 
ment of  water  through  the  plant.  The  formation  of  maltose 
from  starch  in  germinating  seeds  is 
typical  of  the  chemical  reactions.  The 
latter  reactions,  including  many  of  un- 
known nature,  form  the  basis  of  the  fas- 
cinating and  very  important  subject  of 
biochemistry^  or  the  chemistry  of  living 
things. 

Structure  and  Properties  of  the 
Plant  Cell.  The  cells  of  the  leaf  hairs 
of  the  squash  should  be  examined  under 
the  microscope.  We  shall  then  be 
better  able  to  understand  the  reactions 
which  occur  in  it.  Figure  47  shows 
the  structure  of  one  of  the  cells  com- 
posing such  a  tissue.  What  four  or- 
named  in  the  figure?  The  structure 
of  the  cell  may  be  roughly  likened  to  that  of  a  football, 
the  cell  wall  corresponding  to  the  cover,  the  protoplasm  to 
the  bladder,  and  the  vacuole  to  the  air  space  within  the  ball. 
In  chemical  composition,  the  walls  consist  of  cellulose  and 
related  compounds,  the  protoplasm  is  a  complex  mixture  of 
proteins  and  fats,  together  with  other  organic  compounds 
and  inorganic  salts,  and  the  vacuole  contains  sap.  This 
sap  is  a  solution  of  sugars,  salts  and  other  compounds  in 
water.  Suspended  in  the  protoplasm  is  a  body  called  the 
nucleus,  which  is  especially  important  in  the  process  of  repro- 
duction of  the  plant.     It  consists  largely  of  nucleo-proteins. 


yAcuoie-L\ ,, . 

w 


Figure  47.      A  plant  cell 
and  its  principal  parta. 


gans 


do 


you 


find 


12— 


178  CHEMISTRY  OF  THE  FARM  AND  HOME 

The  power  of  soft,  succulent  tissues,  such  as  those  of 
cabbage  seedUngs,  to  stand  erect  is  due  to  the  turgidity  of 
the  separate  cells.  Turgidity  is  caused  by  the  presence  of 
sufficient  water  in  the  vacuole  to  press  the  protoplasm 
against  the  cell  wall  and  distend  the  latter  like  an  inflated 
football.  Have  you  observed  how  quickly  young  plants 
wilt  on  hot,  dry  days?  Wilting  occurs  when  the  air  takes 
water  from  the  plant  faster  than  the  plant  can  get  it  from 
the  soil.  Each  cell  loses  its  turgidity  and  the  whole  plant 
collapses  or  wilts.  When  the  condition  becomes  extreme, 
the  protoplasm  withdraws  from  the  cell  wall  and  shrinks  to 
a  spherical  mass.  This  change  is  called  plasmolysis.  If 
long  continued,  it  causes  death.  From  what  has  preceded 
we  should  appreciate  the  importance  of  water  and  the 
protoplasm  in  the  life  of  the  plant.  We  should  remember 
especially  that  the  most  important  chemical  reactions  of 
the  plant  occur  in  the  protoplasm.  If  one  compares  the 
plant  with  a  busy  chemical  laboratory,  as  one  may  well  do, 
the  protoplasm  may  be  regarded  as  an  apparatus  combining 
the  uses  of  a  crucible,  a  beaker,  and  a  retort.  From  materials 
conveyed  to  it  from  without  the  cell,  it  produces  foods. 
These  are  either  burned  as  fuel  to  drive  the  machinery  of 
the  cells  or  used  as  structural  materials  in  the  processes  of 
growth.  As  the  plant  ages  new  cells  are  formed  to  replace 
the  old  ones  and  to  continue  the  growth  and  work  of  the 
tissues.  Meantime,  the  older  cells  die  and  lose  their  con- 
tents of  sap  and  protoplasm.  The  cell  walls  also  gradually 
thicken  on  account  of  an  increased  production  of  cellulose 
compounds.  This  process,  called  lignification,  modifies  some 
cells  so  that  they  become  practically  solid  and  form  dense 
wood. 

The  chemical  changes  which  occur  in  the  plant  during 
the  round  of  its  growth  from  germination  to  fruitage  will 
now  be  considered.  It  will  be  best  to  choose  as  the  starting 
and  finishing  point  in  this  cycle  the  stage  when  the  plant 


THE  PLANT  AND  ITS  PRODUCTS  179 

is  most  nearly  at  rest.  Can  you  not  suggest  what  stage 
should  be  chosen?  When  the  farmer  plants  his  seed  in  the 
ground  he  hopes  for  the  early  rain  which  he  knows  will 
hasten  germination  and  the  appearance  of  his  crop.  Has 
it  occurred  to  you  how  the  rain  acts  to  produce  this  result? 
Before  answering  this  question  one  must  consider  the 
possibility  that  the  seed  may  act  upon  the  water  also. 
It  can  be  shown,  indeed,  that  seeds  take  up  water  with  great 
force;  for,  if  dry  pea  seeds  be  suitably  confined  and  then 
soaked  in  water,  the  power  with  which  they  will  swell  may 
be  caused  to  lift  great  weights.  This  is  due  to  the  affinity 
of  the  seed  and  the  water  for  each  other.  Both  physical 
and  chemical  attraction  between  the  compounds  of  the 
seed  and  the  water  enter  into  this  affinity.  Do  you  not 
see  that  this  force  must  exceed  the  demand  of  the 
soil  particles  for  water  before  the  seed  can  derive  its  water 
from  the  soil? 

When  the  seed  has  absorbed  a  certain  amount  of  water 
the  chemical  changes  of  growth  begin.  The  rate  at  which 
they  proceed  will  be  greatly  influenced  by  the  temperature, 
Uke  other  chemical  reactions.  Water  alone,  however,  is 
not  sufficient  to  supply  the  needs  of  germination.  By  test- 
ing the  air  surrounding  seeds  germinating  in  a  suitable 
vessel  it  can  be  shown  that  carbon  dioxide  is  produced. 
How  would  you  make  the  test?  The  seeds  respire,  as  do 
animals,  in  the  process  commonly  called  breathing.  What 
element  of  the  air  is  used  in  this  process?  Water  absorbs 
much  heat.  Now,  it  is  good  farm  practice  to  remove  the 
excess  of  water  and  admit  air  by  draining  the  soil.  Can 
you  not  state  two  definite  reasons  why  such  practice  favors 
germination? 

Enzymes  are  very  important  in  the  germination  of  seeds. 
They  are  organic  substances  produced  by  the  protoplasm. 
As  it  is  not  yet  possible  to  obtain  them  in  a  pure  state, 
their    composition    is    unknown.     Enzymes    have    peculiar 


180 


CHEMISTRY  OF  THE  FARM  AND  HOMS 


ENDOSPEPM 


EMBRYO 


abilities  to  cause  various  compounds  to  break  into  simpler 
units.  In  some  cases  they  can  build  compounds  from  units. 
They  cause  various  reactions,  but  the  most  common  ones 
are  those  in  which  the  compounds  affected  take  on  water 
before  breaking  up.  This  reaction  is  called  hydrolysis. 
It  is  exemplary  of  the  great  importance  of  water  in  the 
chemical  changes  of  growth.  Each  kind  of  enzyme  can 
affect  but  one  kind  of  compound.  Thus,  the  enzyme 
which  acts  on  protein  can- 
not act  on  any  other  com- 
pound. These  active  sub- 
stances are  very  sensitive 
to  many  chemical  com- 
pounds and  to  heat.  Some 
compounds  affect  them  like 
poisons  and  temperatures 
of  70°  to  80°C.  perma- 
nently destroy  their  power. 
With  proper  conditions  of 
temperature,  moisture,  and 
oxygen  supply,  the  various  food  compounds  stored  in 
the  endosperm  of  the  seed  are  changed  into  soluble  pro- 
ducts. These  products  are  taken  from  the  sap  by  the  em- 
bryo or  seedling  and  used  for  growth  in  the  manner  already 
described. 

After  germination  has  proceeded  a  few  days,  one  finds 
that  a  small  plant  with  separate  organs  has  been  produced. 
Suppose  the  plant  were  kept  in  darkness.  Would  it  grow 
to  maturity?  Would  the  food  in  the  seed  keep  it  growing? 
Under  the  usual  conditions,  the  roots  and  leaves  take  up 
their  work  as  organs  of  the  plant.  The  stem  is  of  service 
also,  and  later  the  blossoms  and  fruit  appear  and  perform 
the  work  of  reproduction. 

Roots  perform  a  very  important  service  to  plants  by 
absorbing  water  and  dissolved  salts  from  the  soil.     Care- 


Figure  48.  Section  through  a  grain  of 
wheat.  The  embryo  is  the  future  plant. 
The  endosperm  supplies  it  with  sugar 
and  the  bran  layer  surrounding  the 
whole  supplies  ash  constituents.  This 
endosperm  is  rich  in  starch.  In  sorne 
seeds  the  endosperm  is  rich  in  protein 
and  fat. 


THE  PLANT  AND  ITS  PRODUCTS  181 

fully  remove  a  seedling  of  radish  which  has  been  grown  in 
loose  sand,  and  you  will  find  a  conical  mass  of  the  soil  cling- 
ing to  the  root.  On  gently  washing  away  this  cone  it  can 
be  seen  that  it  was  supported  by  short  branches  from  the 
main  root.  These  branches  are  called  root  hairs.  They 
are  confined  to  the  growing  part  of  the  main  root,  just 
behind  its  tip.  Figure  49  shows  the  relation  between  the 
two.     Notice  that  each  root  hair  is  the  arm  of  a  cell  on  the 

surface  of  the  root.  It  coils 
about  the  soil  particles. 
Thus,  if  substances  can  pass 
through  cell  walls,  they  have 
direct  channels  into  the 
plant  through  the  root  hairs. 
Osmosis  is  one  of  the  forces, 
which    will    cause   water  to 

Figure  49.     Section  across  a  root.    The  .  .  . 

contents    of    the    root    hairs    finally       mOVC  mtO  plant  rOOtS.       i  hlS 
reach  the  conducting  bundles  at   the 

center  and  travel  upward  to  the     lorcc  may  be  demonstrated 

by  distending  an  animal 
bladder  with  water,  closing  tightly  and  immersing  in 
molasses.  After  a  few  hours  the  bladder  will  be  shrunken 
and  collapsed.  The  affinity  of  sugar  for  water  is  so  great 
that  the  molasses  is  thirsty.  Sugar  cannot  pass  readily 
through  the  bladder,  but  water  can,  and  hence  the  latter  is 
withdrawn  from  the  bladder.  The  shrinkage  of  pickles  and 
meats  in  brines  is  due  to  the  removal  of  water  by  osmosis. 
When  the  sap  of  root  hairs  contains  much  dissolved  matter, 
the  root  can  take  up  water  by  osmosis.  Root  hairs  also 
absorb  water  by  the  affinity  of  their  cell  walls  and  protoplasm 
for  water.  The  entrance  of  salts  into  the  root  is  not  regulated 
by  the  entrance  of  water,  but  largely  by  the  protoplasm. 
Sometimes  this  organ  allows  a  given  salt  to  pass  through  it, 
and  again  it  does  not.  When  any  salt  enters  the  cell  it  does 
so  by  the  principle  of  osmosis,  if  its  strength  in  the  cell  sap 
is  less  than  in  the  soil  solution. 


182 


CHEMISTRY  OF  THE  FARM  AND  HOME 


The  root  is  not  limited  to  a  selection  from  the  salts  of 
the  soil  water.  It  directly  increases  the  amount  of  salts 
dissolved  from  the  soil  minerals  by  excreting  carbon  diox- 
ide. This  increases  the  solvent  power  of  the  soil  water. 
The  activities  of  the  root  which  we  have  been  considering, 
and  probably  others  unknown,  contribute  to  a  selective 
feeding  power  of  the  plant.  Have  you  noticed  how  rasping 
to  the  touch  are  the  leaves  of  corn,  barley,  and  many  other 


n 


••»  _i 

'1 

li' 

■W'H 

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Figure  50.  Showing  that  rape  and  buckwheat,  on  the  right,  can  absorb  insoluble 
phosphate  better  than  corn  or  barley,  on  the  left.  Left  hand  jar  of  each  pair 
contained  rock  phosphate;  right  hand  jar  contained  acid  phosphate. 

Courtesy  of  E.  Truog,  Soil  Dept.  University  of  Wis. 

grasses?  This  is  due  to  their  peculiar  selection  of  silicon 
from  the  soil.  On  account  of  such  peculiar  ability  also, 
the  rutabaga  and  other  cruciferae  excel  plants  of  other 
families  in  absorbing  phosphates  from  the  soil. 

The  stem  of  the  plant,  together  with  its  branches,  is 
of  chief  interest  to  us  as  the  channel  wherein  sap  and  water 
move.  Have  you  ever  noticed  the  threads  which  protrude 
from  the  pith  when  mature  corn  stalk  is  broken?  They 
contain  the  sap  and  water  channels  arranged  in  bundles.  In 
stems,  which,  like  the  corn  stalk,  grow  toward  the  center,  the 
less  frequent,  newer  bundles  toward  the  center  are  most  ac- 
tive. On  the  other  hand,  in  stems  which  grow  outward  by 
annual  layers,  like  the  common  fruit  tree,  the  active  bundles 
occur  only  in  the  cambium  or  inner  bark.     Figure  51  shows 


THE  PLANT  AND  ITS  PRODUCTS  183 

the  nature  of  the  conducting  bundles.  Water  travels  upward 
in  the  large  thin-walled  vessels  and  the  food-bearing  sap 
travels  about  in  the  smaller  ones.  These  bundles  end, 
on  the  one  hand,  in  the  growing  region  of  the  root  near  the 
root  hairs,  and,  on  the  other,  in  the  loose  tissue  of  the  leaf 
or  flower.  The  arrangement  permits  circulation  in  the  plant. 
Some  stems,  such  as  the  tree  trunks,  tubers,  and  bulbs, 
serve  for  the  storage  of  starch  and  other  foods.     The  reserve 

food  in  the  underground  stem 
of  the  quack  grass  makes  this 
weed  very  resistant  to  tillage. 
The  leaf  is,  from  the  chem- 
ist's point  of  view,  the  most 
interesting  organ  of  the  plant. 
This  is  because  it  frees  the 
young  plant  from  dependence 
upon  the  parent  seed.  When 
this  organ  emerges  from  the 
soil,    two    important  processes 

Figure  61.     A  conducting  bundle  of  a         ,     .         ,^v  __,        i       /.  i  . 
stem.     The  laige  channels  (w)  con-  Set    m:   (1)  i  he  leai  lOSCS  Water 
vey  water  to  the  leaves.    The  smaller  ,         .|           .           mi  •      i 
channels,  grouped  at  the  top  of  the  tO    the  air.        1  hlS   lOSS   IS    trans- 
figure, convey  food-laden  sap  from  -            ,    .                ,    . ,              •!    x i  i 

the  leaves  to  other- parts  of  the  lerred  toward  the  SOU  through 

the  stem.  It  is  finally  bal- 
anced by  entrance  of  water  from  the  soil  to  the  root. 
This  introduces  the  absorption  of  water  and  nutrient  salts 
by  the  plant,  the  first  step  independent  of  the  mother  seed: 
(2)  The  leaf  turns  green.  This  coloring  is  due  to  the  pro- 
duction of  the  compound  chlorophyll  by  the  action  of  light. 
It  requires  the  presence  of  oxygen  and  iron.  The  true  life 
work  of  the  plant  now  begins.  When  exposed  to  the  light, 
chlorophyll  has  the  peculiar  ability  to  cause  water  and 
carbon  dioxide  to  combine.  We  have  traced  from  the  soil 
to  the  leaf  the  course  of  the  water  necessary  to  this  proc- 
ess. The  carbon  dioxide  required  enters  the  leaf  from  the 
surrounding  air  through  the  stomata.     These  are  also  the 


184 


CHEMISTRY  OF  THE  FARM  AND  HOME 


channels  by  which  water  escapes  from  the  leaf  to  the  air. 
A  single  stoma  is  shown  in  surface  and  side  view  in  Figure 
52.  With  the  aid  of  the  microscope  you  can  readily  find 
stomata  on  the  peeled-off  epidermis  of  any  common  leaf. 
With  most  leaves  they  are  of  greatest  number  on  the  under 
side.  Note  from  the  illustration  that  the  opening  of  the 
stoma  leads  from  the  outer  air  into  a  chamber  in  the  leaf. 

This  chamber  is  surround- 
ed by  loose  tissue.  Carbon 
dioxide  diffuses  from  this 
space  into  the  leaf  tissue 
and  through  the  moist 
walls  of  the  separate  cells. 
Together  with  water  it 
now  comes  under  the  in- 
fl  u  e  n  c  e  of  chlorophyll. 
The  following  equations 
may  be  written  to  express  the  chief  result  of  this  process, 
called  photosynthesis: — 


Figure  52.  A  stoma  as  seen  under  the 
microscope.  On  the  left,  looking  at  the 
surface  of  the  leaf.  On  the  right,  looking 
at  the  edge  of  a  leaf  cut  through  the  stoma. 


CO2    +  H2O 


HCHO  +  O2 

Formaldehyde 


6  HCHO        -^  C6H12O6 
Formaldehyde     Dextrose 

Have  you  figured  out  the  derivation  of  the  word  photo- 
synthesis? The  equations  may  not  express  just  what 
occurs  in  the  process.  They  are  merely  expressions  of  the 
most  important  steps  which  seem  likely  to  occur  in  produc- 
ing the  first  carbohydrate  of  the  plant.  As  already  stated, 
this  carbohydrate  is  either  burned  as  a  source  of  energy  or 
converted  to  reserve  food  compounds.  It  is  not  only  im- 
portant as  fuel  for  the  protoplasm,  but  it  is  essential  to  the 
formation  of  the  building  material,  cellulose.  When  stored, 
it  is  converted  to  sucrose  and  then  to  starch.  When  seeds 
germinate  the  starch  is  converted  to  maltose  and  then  to 


THE  PLANT  AND  ITS  PRODUCTS  185 

dextrose.  What  substance  besides  dextrose  is  produced 
in  photosynthesis,  as  shown  by  the  preceding  equations? 
This  gas  is  partly  used  in  the  leaf  cells  and  partly  escapes 
to  the  air  through  the  stomata.  There  it  balances  some  of 
the  oxygen  removed  by  combustion,  animal  respiration, 
and  other  processes. 

By  chemical  changes  within  the  plant  many  different 
compounds  are  produced  from  the  carbohydrates.  The 
most  important  of  these  are  the  proteins.  In  the  forma- 
tion of  proteins,  nitrates,  sulphates  and  phosphates  are  re- 
duced in  the  leaf  cells.  They  are  then  combined  with 
carbohydrates  or  their  relatives  to  form  unit  parts  of  protein 
molecules.  The  important  reserve  fats  of  the  plant  are 
also  derived  from  carbohydrates.  In  view  of  these  proc- 
esses, is  it  difficult  to  comprehend  the  great  importance 
of  the  leaf  to  the  plant? 

The  flower  and  fruit,  forming  together  the  reproduc- 
tive organ  of  the  plant,  are  the  seat  of  rapid  and  complex 
chemical  reactions.  They  utilize  materials  prepared  by 
the  leaf  and  brought  to  them  in  the  sap  stream.  Depend- 
ent upon  the  nature  of  the  plant,  these  materials  are  con- 
verted chiefly  to  starch,  fat,  or  protein.  These  compounds 
are  stored  in  the  seed  with  the  embryo  of  the  future  plant. 
During  these  processes  much  oxygen  is  absorbed  and  car- 
bon dioxide  is  excreted.  This  is  due  to  the  respiration  or 
burning  of  the  protoplasm  as  it  does  its  work.  In  some  plants 
the  heat  produced  in  this  way  keeps  the  temperature  of  the 
flower  considerably  above  that  of  the  surrounding  air. 

The  production  of  a  mature  seed  is  the  great  end  of 
active  plant  growth.  It  does  not,  however,  mark  the  end 
of  physical  and  chemical  changes.  Respiration  and  attend- 
ant changes  go  on  slowly  in  the  seed  so  long  as  it  is  capable 
of  reproduction. 

Plant  nutrition.  The  growing  plant  must  be  fed.  Water 
and  carbon  dioxide  are  incapable  of  maintaining  growth. 


186 


CH EMI 8 TRY  OF  THE  FARM  AND  HOME 


The  plant  must  have  food  compounds  from  the  soil.  This 
can  be  shown  readily  by  the  failure  of  plants  to  grow  in  pure 
water.  The  study  of  what  elements  are  necessary  for  the 
complete  growth  of  the  plant  and  how  each  affects  its  growth 
is  called  plant  nutrition.  This  study  has  been  followed 
chiefly  by  growing  the  plant  in  pure  water  or  pure  sand 

to  which  food 
salts  have  been 
added.  This 
method  is  called 
water  or  sand  cul- 
ture, respective- 
ly. It  has  the 
advantage  over 
the  soil  that  one 
can  know  just 
what  compounds 
are  supplied  to 
the  plant. 

The  various 
elements  found 
in  plants  grown 
in  the  soil  have 
been  divided 
into  essential  and 
unessential.  An 
essential  element 
is  one  necessary  for  the  complete  development  of  the  plant 
from  one  generation  to  the  next. 

The  water  cultures  illustrated  in  Figure  53  show  the 
effect  of  a  complete  lack  of  some  of  these  elements.  Refer 
to  the  list  of  elements  in  Table  V  and  check  sodium,  chlorine, 
and  silicon.  These  are  the  unessential  elements.  All  of 
the  other  elements  of  the  list  are  essential  to  plants.  Ni- 
trogen causes  vigorous,  leafy  development.     Potassium  and 


1 

Figure  53.  Young  corn  plants  growing  in  water  culture. 
On  the  left,  in  water  only.  On  the  right,  with  essen- 
tial salts  added. 


THE  PLANT  AND  ITS  PRODUCTS 


187 


calcium  are  essential  to  carbohydrate  formation  and  the 
building  of  cell  walls.  Phosphorus  hastens  ripening  of  the 
seed.  You  will  find  mentioned  early  in  this  chapter  three 
very  important  compounds  in  which  magnesium,  sulphur 
and  phosphorus  occur.     Iron  is  essential  to  the  production 

of  one  of  them.  The  unes- 
sential elements  which  you 
have  checked  are  sometimes 
beneficial  to  plants. 

Crops,  or  plants  in  bulk, 
as  the  farmers  grow  them, 
have  different  habits  of 
growth  and  food  require- 
ments. Thus,  the  legumes 
obtain  nitrogen  directly 
from  the  air  in  the  soil; 
but  no  other  plants  can  do 
so.  Alfalfa,  clover,  beans, 
and  peas  are  leguminous 
plants.  They  support  and 
nourish  in  nodules  of  their 
roots  certain  bacteria.  These 
bacteria  form  nitrogen  com- 
pounds from  the  soil  air  and 
present  them  to  their  hosts. 
Thus,  while  these  plants  need 
much  calcium  and  potassium, 
they  require  practically  no  nitrogen  compounds  from  the  soil. 
The  cereal  grains,  such  as  wheat,  barley,  and  corn,  belong 
to  the  grass  family  of  plants.  This  family  is  dependent 
upon  manuring,  and  especially  so  for  nitrogen.  Barley 
and  the  true  grasses  are  shallow  rooted  and  soon  exhaust 
the  food  of  the  surface  soil.  These  crops  need  phosphorus 
for  seed  production,  and  they  use  much  potassium.  Where 
heavy  leaf  growth  is  most  desired,  as  when  they  are  cut 


Figure  54.  Root  nodules  on  the  roots 
of  a  soy-bean  plant.  By  the  aid  of 
bacteria  living  in  these  nodules  clover 
and  the  other  plants  of  the  legume 
family  take  nitrogen  from  the  air  in 
the  soil. 


188  CHEMISTRY  OF  THE  FARM  AND  HQME 

immature  for  hay,  the  soil  must  contain  a  good  supply  of 
nitrogen  compounds,  These  will  form  by  the  decay  of  le- 
gume crops  or  farm  manure.     Nitrate  salts  can  be  added  also. 

Root  crops  include  the  turnip,  beet,  and  similar  plants. 
These  produce  large  amounts  of  reserve  compounds  and 
are  heavy  feeders.  This  fact  is  especially  true  of  the  mangel, 
a  relative  of  the  sugar  beet.  The  root  crops  are  very  de- 
pendent upon  the  fertility  of  the  soil  for  supplies  of  food 
materials.  For  the  different  species  of  beets,  a  deep,  fertile 
soiPis  necessary.  Many  of  the  truck  crops,  such  as  the  cab- 
bage, and  onion,  resemble  the  root  crops  in  feeding  habits. 

Fruit  and  nut  trees  and  forest  growth  contain  much  re- 
serve food  materials  in  their  trunks  or  stems.  They  draw 
chiefly  upon  this  reserve  for  their  growth  from  year  to  year. 
A  large  supply  of  food  in  the  soil  is  thus  unnecessary  for 
these  plants.  The  annual  fall  of  leaves  and  twigs  in  the 
forest  is  almost  sufficient.  Small  fruit  plants,  however, 
such  as  the  strawberry,  which  have  little  reserve  food,  re- 
spond  liberally   to   manuring. 

Harvesting,  to  be  conducted  wisely,  must  occur  at  the 
time  when  a  crop  has  the  highest  food  value.  With  most 
of  the  grain  crops  this  point  occurs  at  full  ripeness.  At  this 
stage  the  food  materials  of  the  stem  have  moved  into  the 
seed.  The  stem  is  then  woody  and  indigestible.  With 
true  hay  crops  and  cereal  grains  cut  for  hay,  such  as  oats, 
the  stems  and  leaves  contain  more  protein  and  less  cellulose 
at  early  blooming  than  at  maturity.  It  is  an  economic  loss 
to  the  farmer  who  does  not  observe  this  fact. 

Corn  differs  from  the  other  grains  in  that  its  most  val- 
uable constituent,  starch,  is  stored  in  the  seed  rapidly  at 
the  last  stage  of  ripening.  During  the  period  when  the  ears 
are  glazing  starch  increases  ten  per  cent  in  the  plant,  while 
the  amount  of  cellulose  remains  unchanged.  Whether 
cut  for  grain  or  silage,  therefore,  corn  should  be  mature. 

Silage  is  better,  too,  from  mature  than  from  immature, 


^HE  Plant  and  its  products 


189 


corn,  because  its  composition  changes  less  in  the  silo.  What 
differences  have  you  noted  between  the  odor  and  flavor  of 
corn  and  of  silage?  Those  differences  are  due  partly  to  oxi- 
dation in  the  silo.  They  accompany  changes  of  sugar  to 
acids  and  alcohols  and  the  breaking  down  of  protein.  Such 
changes  decrease  the  food  value  of  the  corn  and  should  be 
checked.     Will   a   loose,    rickety   silo   check   them?     How 

will  loose  fining 
of  the  silo  affect 
them?  Even 
when  air  is  ex- 
cluded the  living 
cells  of  the  fresh 
silage  continue 
to  respire,  using 
the  oxygen  of 
some  of  their 
compounds. 
Would  this  proc- 
ess continue  longest  in  silage  from  mature  or  immature 
corn?  The  best  quality  and  highest  food  value  is  secured 
by  putting  nearly  mature  corn  into  the  silo. 

Exposure  to  rain  and  overhandling  cause  much  loss 
of  food  value  to  hay  crops.  This  loss  is  greatest  with  the 
value  of  clover  and  alfalfa  hays.  The  delicate  leaves  of 
these  crops  easily  rattle  off  when  they  are  dry  and  brittle. 
Since  the  leaves  contain  more  protein  and  much  less  cellulose 
than  the  stems,  the  hay  loses  most  of  its  value  in  this  way. 
Timely  cutting  and  prompt  curing  are  thus  very  important. 
Means  by  which  the  composition  of  crops  can  be  improved 
have  been  sought  for  many  years.  Man  has  been  seeking 
to  increase  the  amount  of  sugar  in  the  sugar  beet,  the  per- 
centage of  protein  in  wheat,  and  so  on.  At  first  thought 
it  would  seem  that  the  amount  or  kind  of  fertilizers  might 
produce  desirable  changes  of  this  sort.     It  has  been  clearly 


Figure  55.     Measuring  the  amount  of  sucrose  in  sugar 
beets  by  means  of  the  polariscope. 


190      CHEMISTRY  OF  THE  FARM  AND  HOME 

shown,  however,  that  the  plant  food  in  the  soil  influences 
the  amount,  rather  than  the  kind  of  growth  of  plants. 
This  is  especially  true  of  the  seed,  for  the  plant  tends  strong- 
ly to  produce  seed  always  of  the  same  composition.  If 
any  food  element  is  lacking,  it  produces  less  seed  rather 
than  seed  of  unusual  composition.  As  a  result  of  heredity, 
or  the  inheritance  of  qualities,  a  great  deal  of  improvement  in 
crops  has  been  secured  by  selection  and  breeding. 

Environment.  Heredity  is  powerful;  but  it  is  not  so 
powerful  as  environment  in  affecting  the  composition  of 
crops.  By  environment  we  mean  the  climate;  and  climate 
consists  of  sunshine,  rainfall,  temperature,  and  other  factors. 
No  matter  what  the  inheritance  of  the  farmer's  seed,  no 
matter  how  he  may  fertilize,  he  cannot  overcome  the  influ- 
ence of  environment  upon  his  crop.  To  increase  the  sugar 
content  of  his  sugar  beets,  for  example,  he  must  breed  or 
select  seed  in  the  region,  or  climate,  where  he  is  to  grow 
the  crop.  One  of  the  most  important  effects  of  climate 
is  due  to  excessive  rainfall  or  irrigation.  From  hard  wheat 
grains  rich  in  protein  this  condition  produces  plump  soft 
grains,  rich  in  starch  and  less  suited  to  bread-making. 
Temperature  is  especially  important  in  the  growth  of  sugar 
beets  and  sugar  corn.  These  crops  are  favored  by  the 
temperate  heat  of  the  northern  states  of  our  country. 

Rotation  of  crops  has  come  to  be  known  as  a  necessary 
feature  of  the  successful  farmer's  program.  Its  value 
lies  partly  in  the  checking  of  particular  diseases  which  in- 
crease where  the  particular  crops  which  they  attack  are 
cultivated  continuously.  But  it  is  also  a  means  of  greatly 
improving  the  physical  condition  and  the  fertility  of  the 
soil.  After  the  growth  of  shallow-rooted  crops,  such  as 
barley  and  turnips,  the  land  needs  the  deep  tillage  required 
by  the  potato  and  mangel.  When  the  deep-rooted  mangel 
is  harvested,  its  leaves  return  to  the  surface  soil  much  plant 
food  obtained  from  its  deeper  portions. 


THE  PLANT  AND  ITS  PRODUCTS  191 

Have  you  observed  any  difference  of  prosperity  between 
farmers  who  grow  clover  in  crop  rotations  and  those  who  do 
not?  Perhaps  you  have  asked  your  father  or  some  pros- 
perous neighbor  why  he  grows  clover  in  preference  to  common 
grasses.  Not  all  successful  farmers,  however,  know  just 
why  clover  earns  them  profits.  It  is  because  this  plant, 
like  the  other  legumes,  adds  nitrogen  compounds  to  their 
soils.  The  roots  and  stubble  of  one  year's  growth  of  clover 
or  alfalfa  on  an  acre  of  land  leave  fifty  or  sixty  pounds  of 
nitrogen  in  the  first  nine  inches  of  soil.  This  is  enough  for 
a  cereal  grain  crop.  Peas  and  beans  leave  only  a  few  pounds 
of  nitrogen  in  their  small  root  systems;  but,  when  their  tops 
are  plowed  in,  they  supply  enough  for  one  crop  of  any  but 
the  heaviest  feeding  truck  and  root  crops.  Can  you  learn 
from  any  helps  how  much  that  is?  The  importance  of  clover 
and  other  legumes  on  the  farm  should  be  plainly  seen  when 
one  knows  that  other  crops  are  helpless  to  secure  free  ni- 
trogen from  the  soil. 

SUMMARY 

The  plant  serves  as  a  factory  for  converting  compounds  of  the 
soil  and  air  into  food  for  animals.  When  mature  it  contains  sixty 
to  ninety  per  cent  of  water.  The  other  constituents  consist  of  organic 
compounds  and  a  little  ash-forming  material.  Carbohydrates  are 
the  most  abundant  of  the  organic  compounds.  They  are  produced 
in  the  leaves  and  serve  as  food  and  building  material.  Fats  are  stored 
in  seeds  as  foods.  Proteins  are  stored  also  in  the  seed.  They  differ 
from  fats  and  carbohydrates  in  that  they  contain  nitrogen,  sulphur, 
and  sometimes  phosphorus.  The  changes  of  life  and  reproduction  are 
very  closely  dependent  on  proteins.  Ash  compounds  are  the  remains 
of  salts  taken  from  the  soil. 

Active  growth  begins  with  the  sprouting  of  the  seed.  First,  the 
seed  absorbs  much  water  from  the  soil.  Then,  if  the  soil  is  warm  and 
well  aired,  enzymes  begin  to  act.  These  are  substances  which  change 
starch  and  other  foods  of  the  seed  to  simpler  food  compounds.  The  em- 
bryo or  young  plant  grows  and  develops  the  root,  leaf  and  other  organs. 

The  roots  of  plants  absorb  water  and  food  salts  from  the  soil. 
They  have  some  power  to  select  the  salts  taken  up.  Green  leaves 
absorb  carbon  dioxide  from  the  air.     They  also  give  off  water  to  the 


192      CHEMISTRY  OF  THE  FARM  AND  HOME 

air.  This  loss  keeps  water  moving  through  the  plant  from  the  soil. 
Chlorophyll,  the  green  compound  of  the  leaf,  forms  carbohydrate 
from  carbon  dioxide  and  watei-  in  light.  The  stem  and  branches  con- 
tain channels  in  which  water  moves  to  the  leaves  and  sap  moves  from 
them.  When  the  blossoms  and  the  fruits  are  forming,  the  sap  suppUes 
them  with  food  compounds. 

Farm  crops  differ  widely  in  habits  of  growth  and  of  food  require- 
ments. In  harvesting  them  it  is  important  to  choose  that  stage  of 
growth  when  they  have  the  highest  food  value.  Silage  undergoes 
some  important  changes  due  to  respiration  of  the  cells,  or  unit  struc- 
tures, of  the  immature  plants.  Chmate,  especially  temperature, 
afifects  the  composition  of  crops  more  than  inheritance  or  the  manner 
of  feeding  them.  Crops  should  not  be  grown  continuously,  because 
such  practice  favors  plant  diseases  and  reduces  soil  fertihty  unevenly. 
Crop  rotation  prolongs  the  fertility  of  the  soil  and  improves  the  crops. 
Clover  and  other  legume  plants  are  indispensable  in  crop  rotations, 
because  they  supply  nitrogen  compounds  to  the  soil. 

QUESTIONS. 

1.  In  what  two  conditions  does  water  exist  in  green  plants? 

2.  What  is  the  composition  of  dextrose? 

3.  Of  what  use  is  sucrose  to  the  growing  plant? 

4.  How   can   the   starch   of   different   plants   be   distinguished? 

5.  What  is  the  chemical  structure  of  fats? 

6.  What  two  chemical  elements  not  present  in  either  carbo- 
hydrates or  fats  are  contained  in  protein  molecules? 

7.  Which  of  the  plant  compounds  are  most  closely  associated 
with  chemical  life  processes? 

8.  Name  five  elements  abundant  in  the  ash  of  plants? 

9.  What  are  the  chief  organs  of  a  plant  cell?  What  is  the 
composition   of   each? 

10.  What  is  the  cause  of  wilting? 

11.  What  are  the  nature  and  action  of  enzymes? 

12.  What  organ  of  the  cell  regulates  the  entrance  of  soil  com- 
pounds into  the  root  hairs? 

13.  Name  two  elements  which  must  be  present  for  the  produc- 
tion of  chlorophyll? 

14.  Describe  photosynthesis. 

15.  What  chemical  elements  are  essential  to  growth  of  plants? 

16.  What  is  the  difference  between  legumes  and  other  families 
of  plants  in  regard  to  obtaining  nitrogen? 

17.  Why  should  hay  crops  be  harvested  before  maturity? 

18.  What  process  causes  the  chemical  changes  in  silage? 

19.  What  is  meant  by  environment? 

20.  How  does  it  influence  the  composition  of  crops? 

21.  Why  are  legumes  especially  important  in  crop  rotations? 


CHAPTER  VII 
THE  SOIL 

Origin  of  Mother  Earth.  At  some  time  in  the  far  dis- 
tant past,  according  to  astronomers,  the  material  of  our 
planet  traveled  through  space  as  a  mixture  of  gases.  To 
human  eyes  on  other  planets,  had  there  been  such,  it  might 
have  appeared  like  the  nebular  mists  now  visible  in  certain 
parts  of  the  heavens  through  the  telescope.  This  condi- 
tion could  exist,  of  course,  only  at  very  high  temperatures, 
such  as  might  be  produced,  for  example,  by  the  impact  of 
two  solid  heavenly  bodies.  Gradually  the  gaseous  mass 
cooled.  As  gradually,  also,  certain  chemical  elements  with 
strong  affinities  for  one  another,  but  which  had  been  kept 
apart  by  the  intense  heat,  began  to  combine.  Hydrogen 
combined  with  oxygen  to  form  water.  Silicon  combined 
with  oxygen  to  form  silica.  Calcium  and  oxygen  combined 
to  form  lime.  Silica  and  lime  combined  to  form  a  mineral. 
Thus,  one  after  another,  various  minerals  were  formed  to 
produce  a  solid  crust  thrown  into  folds  which  retained  the 
water.  Such,  in  brief,  is  a  widely  accepted  theory  of  the 
manner  in  which  ''Mother  Earth"  came  into  existence. 

Appearance  of  Life.  In  the  course  of  time,  when  con- 
ditions favored,  certain  of  the  chemical  elements  became 
associated  in  complex  arrangements  endowed  with  life. 
Perhaps  living  things  first  appeared  in  the  water.  The 
earliest  form  may  have  been  much  like  the  simplest  crea- 
tures one  now  finds  in  pond  water  by  the  aid  of  the  micro- 
scope. Suffice  it  to  say  that  it  must  have  been  endowed  by 
the  Supreme  Creative  Intelligence  with  the  chief  powers 
still  characteristic  of  living  beings. 
13—  193 


194      CHEMISTRY  OF   THE  FARM  AND  HOME 

Formation  of  Soil.  Finally  some  of  the  early  forms  of 
life  attached  themselves  to  the  solid  land  for  support. 
Here,  by  the  waste  products  of  their  life  processes  and  by 
the  final  decay  of  their  own  bodies,  they  contributed  to 
the  sum  of  chemical  and  physical  changes  which  continually 
destroy  and  reform  the  soil  minerals.  Gradually  there  were 
established  the  living  conditions  necessary  for  the  higher 
forms  of  life  now  so  widely  distributed  in  the  plant  and 
animal  kingdoms.  Thus  the  development  of  life  has  been 
largely  dependent  upon  the  formation  of  soil.  Through 
countless  ages  the  process  has  been  the  same — a  ceaseless 
movement  of  material  through  chemical  and  physical 
changes.  In  large  part  these  changes  are  biological,  that 
is,  they  are  caused  by  the  living  things  inhabiting  th^  ma- 
terial converted  to  soil.  Is  it  not  clear  to  you  that  the  soil 
is  a  state  of  matter,  rather  than  a  fixed,  unchangeable  por- 
tion of  matter?  It  is  wonderfully  like  a  living  body  in  that 
it  is  continuously  changing  and  renewing  itself.  This  very 
process  is  what  makes  it  fertile.  On  the  one  hand,  rock  and 
plant  fragments  are  continuously  undergoing  destruction. 
Again,  the  products  of  this  destruction  are  continuously 
being  removed  by  draining  away  in  water  or  by  diffusing 
into  the  air.  The  mill  in  which  these  changes  go  on  is  what 
we  commonly  call  ''the  soil." 

As  the  home  of  the  plant  the  soil  has  long  been  recog- 
nized as  of  the  greatest  importance  to  the  maintenance  of 
life  on  the  earth.  Until  the  time  of  the  great  Liebig,  how- 
ever, little  was  known  of  it  in  a  scientific  way.  In  recent 
years  study  of  the  physics  and  chemistry  of  the  soil  has 
shown  it  to  be  one  of  the  most  complex  subjects  in  the 
realm  of  science.  Not  only  are  its  compounds  numerous 
and  still  partly  unknown,  but  it  is  the  medium  of  almost 
endless  physical  and.  chemical  reactions.  It  would  be 
better,  could  we  do  so,  to  avoid  so  complex  a  subject  at 
first.     Yet,  since  knowledge  of  the  soil  is  so  essential  to  our 


THE  SOIL 


195 


further  study,  we  may  best  consider  here  its  most  impor- 
tant features  in  a  simple  manner. 

In  your  daily  labors  and  walks  in  the  fields  have  you 
found  the  appearance  of  the  soil  the  same  from  place  to 
place?  Perhaps  you  have  been  accustomed  to  using  the 
names  sand,  clay  and  muck  for  soils  quite  different  in  ap- 
pearance. Too  often,  though,  these  names  are  used  to 
explain  differences  in  the  soil  which  are  only  vaguely  under- 
stood. There  are  still  too  many 
persons  to  whom  the  soil  is  merely 
''dirt,"  personal  contact  with 
which  seems  degrading.  To  the 
keen  minded  country  boy  or 
girl,  however,  there  can  be  no  ob- 
ject more  wonderful  and  interest- 
ing than  the  soil,  rich  in  variety 
of  minerals  and  teeming  with  living 
things  and  chemical  action. 

Relation  of  Rocks  and  Plants 
to  Soil.     To  an  observant  mind  it 
is  pretty  plainly  evident  that  the 
rocks  and  stones  continually  crop- 
Figure  56.    Justus  von  Liebig,  ping  to  the  surfacc  of    the    soil 
IS^a^c^Lil^'^'ni^r^t  in  tilled  fields    must   have  some 
ftdf  the%ian?  tnd  'that' u  commou  rektiou  to  the  soil.     Has 
should  be  fertilized.  -^    occurrcd   to    you,    also,    that 

the  plants  which  die  and  fall  to  the  ground  year  after 
year  in  marshes  and  swamps  may  have  some  relation 
to  the  deep  black  soils  formed  there?  By  the  aid  of  the 
microscope  one  can  see  plainly  that  the  finer  material 
of  fertile  soils  does,  indeed,  consist  chiefly  of  minute  frag- 
ments of  rock  and  of  plant  tissues.  The  mere  pres- 
ence of  these  materials  does  not,  however,  guarantee  a 
fertile  soil.  In  order  to  contribute  to  fertility  they  must 
be  undergoing  processes  of  decay  which  free  the  essential 


196  CHEMISTRY  OF  THE   FARM  AND  HOME 

elements  which  they  contain.  These  elements,  too,  must 
be  released  as  parts  of  simple  compounds  which  plants  can 
absorb  for  food.  Processes  of  this  kind  are  continually 
going  on  in  fertile  soils.  Some  are  caused  by  physical 
forces,  such  as  pressure  or  heat.  Others  are  caused  by 
chemical  forces,  such  as  oxidation.  The  chemical  forces  are 
due  chiefly  to  the  Uving  things  that  inhabit  the  soil.  Earth- 
worms and  larger  animals  take  part  in  them,  but  the  es- 
pecially active  agents  are  bacteria.  We  may  call  these 
living  things  biological  agents  in  fertility.  They  must  be 
favored  by  proper  physical  and  chemical  surroundings,  if 
the  soil  is  to  be  kept  fertile.  Thus,  while  the  successful 
farmer  must  be  a  practical  engineer  in  the  tilling  and  drain- 
ing of  his  soils,  he  must  also  be  somewhat  of  a  physicist, 
chemist  and  biologist  combined.  It  does  not  require  much 
reflection  for  one  to  realize  that  profitable  husbandry  of  the 
soil  requires  no  small  degree  of  skill. 

Before  taking  up  the  study  of  the  physical  and  chemical 
changes  which  occur  in  the  soil  it.  is  necessary  that  we 
equip  ourselves  with  information  about  its  most  important 
constituents.  For  convenience,  these  may  be  divided  into 
inorganic  constituents  derived  from  rocks  and  organic  ma- 
terials resulting  from  the  decay  of  plants  and  animals.  We 
must  not  suppose  at  all,  however,  that  these  materials 
exist  separately  in  the  soil.  On  the  contrary,  as  decay  goes 
on  the  products  formed  from  inorganic  and  from  organic 
matter  combine  with  each  other  in  intricate  ways. 

Soil  Minerals.  Can  you  recall  whether  or  not  most  of 
the  stones  you  have  picked  up  from  time  to  time  have 
looked  uniform  in  color  and  texture,  as  though  composed 
of  one  substance?  If  not,  examine  some  at  your  first  oppor- 
tunity. You  will  find  that  some  of  them  consist  very 
plainly  of  bits  of  different  kinds  of  rock  cemented  together 
by  yet  other  kinds.  These  separate  constituents  are  min- 
erals.    In  some  places,  as  in  the  iron  and  copper  regions. 


THE  SOIL 


197 


they  occur  in  great  masses.  One  can  distinguish  the  dif- 
ferent minerals  by  differences  in  hardness,  color,  weight 
and  other  properties.  The  study  of  these  differences 
belongs  to  the  special  subject  of  mineralogy.  A  list  of  the 
most  important  soil  minerals  will  now  be  given.  In  order 
that  you  may  learn  their  general  composition  and  what 
essential  elements,  if  any,  they  supply  to  plants  the  acid  and 
base  forming  elements  which  they  contain  are  given  in 
separate  columns.  What  class  of  compounds  have  you 
become  familiar  with  in  your  earlier  study  which  is  formed 
when  acids  unite  with  bases?  From  the  number  of  ele- 
ments present  in  some  of  these  compounds  of  the  soil  you 
can  see  that  they  must  be  quite  complex. 

Table  VI. — Soil  Minerals  and  Their  Constituents 


Mineral 

Base  Forming  Elementa 

Acid  Forming  Elementa 

Quartz . . . 
Kaolinite. 

None 

Silicon 

Aluminium 

Silicon 

Talc 

Magnesium 

Silicon 

Feldspar  . 
Mica 

Aluminium  and  Potassium 

Aluminium  and  Sodium  or 

Aluminium,  Sodium,  Calcium.  . 

Aluminium  and  Potassium 

or 

Aluminium,  Potassium 

•{  Magnesium,  Iron 

Silicon 
Silicon 

or 
Aluminium,  Sodium 

Magnesium,  Iron 

Selenite .  . 

Calcium 

Sulphur 
[Phosphorus  and  Chlorine 

\                 or 

Apatite . . 
Calcite... 

Calcium 

Calcium 

[Phosphorus  and  Fluorine 
Carbon 

Limonite . 

Iron 

None 

Let  us  compare  the  common  properties  of  these  min- 
erals. 

Quartz  or  silicon  dioxide  is  a  very  hard  and  insoluble, 
crystalline  mineral.     Flint  is  a  form  of  quartz.     The  min- 


198      CHEMISTRY  OF  THE  FARM  AND  HOME 

eral  varies  from  white  to  black,  and  some  varieties,  such 
as  rose  quartz,  are  beautifully  colored  by  traces  of  iron 
compounds  or  other  impurities.  It  occurs  frequently  in 
great  masses  and  is  estimated  to  form  about  one  third 
of  the  solid  material  of  the  earth's  crust.  Sand  consists  of 
small  fragments  of  quartz  rolled  smooth  by  the  action  of 
moving  water.  Does  the  composition  of  quartz  give  you 
any  clue  to  the  reason  why  sandy  soils  are  infertile? 

Kaolinite,  hydrated  silicate  of  aluminium  is  one  of  the 
softest  of  minerals.  It  is  white  to  yellowish  in  color.  It  is 
the  chief  constituent  of  clay  soils.  By  its  peculiar  affinity 
for  water  it  greatly  influences  the  texture  of  the  soil.  It 
thus  causes  clay  soils  to  ''puddle"  to  a  pasty  mass  when 
thoroughly  wet.  The  behavior  is  a  useful  one  in  the  pot- 
tery and  brick  industries  but  quite  the  opposite  in  soils. 
Does  kaolinite  supply  plant  food? 

Talc,  magnesium  silicate,  is  a  very  soft  mineral.  Since 
all  other  minerals  scratch  it,  its  hardness  is  taken  as  the 

standard  in  mineral  ogy  and  given 
the  value  of  unity,  or  one.  It  is 
white  to  green  in  color  and  feels 
soapy  to  the  touch.  The  soap- 
stone  commonly  used  in  making 
furnaces,  sinks  and  laboratory 
table  tops  is  a  variety  of  talc.  It 
is  estimated  that  talc  forms  about 
5  per  cent  of  the  minerals  of  the 
earth's  surface.  It  is  slowly  de- 
Figure  57.    Photomicrograph  of  composcd  by  the  soil  watcr. 

oUgoclase,     a    sodium     bearing  t-.  7  j    . 

feldspar,  showing  the  composite         reidspar    IS    a    group     name 

character  of  some  minerals.  „  ,  •  ,  ^  •    ^ 

Courtesy  Prof.  A.  N.  wincheii.  of  scvcral  mmcrals  which  are 
very  important  in  the  soil.  They  are  the  chief  minerals  of 
many  kinds  of  rocks,  but  especially  granite,  where  they  are 
commonly  associated  with  quartz  and  mica.  The  most 
important  feldspar  is  orthoclase.     This  is  a  silicate  of  po- 


THE  SOIL     .  .  199 

tassium  and  aluminium.  It  is  a  hard,  flesh-colored  mineral. 
It  is  much  more  soluble  in  water  than  either  quartz  or 
kaolinite.  Can  you  not  suggest  why  such  a  property  con- 
tributes to  the  formation  of  fertile  soils  from  feldspar? 
The  feldspars  are  estimated  to  form  about  one  half  the 
minerals  of  the  earth's  crust.  Many  other  silicate  minerals 
are  closely  related  by  composition  to  the  feldspars. 

Mica  is  the  group  name  for  several  rather  soft  minerals 
which  are  much  less  soluble  than  the  feldspars.  These 
minerals  are  polysilicates.  That  is,  the  acid  portion  of 
their  molecules  consists  of  a  multiple  of  the  simple  silicic 
acid  molecule.  This  is  the  cause  of  their  capacity  to  hold 
several  base  forming  elements  together. 

The  most  characteristic  property  of  mica  is  the  readiness 
with  which  it  splits  into  sheets.  You  may  have  seen  sheets 
of  the  mineral,  gray  to  black,  fitted  into  the  upper  walls  of 
coal  stoves.  The  different  varieties  of  mica  may  form 
together  one  twelfth  of  the  earth's  minerals.  Can  you 
suggest  why  they  are  important  in  soils? 

Selenite  is  a  soft,  rather  light  mineral  and  white  to 
reddish  in  color.  It  occurs  in  small  crystals  in  nearly  all 
rocks.  In  some  places  it  occurs  in  masses.  This  form  of 
it,  called  gypsum,  is  pulverized  to  form  "land-plaster." 
Selenite  is  much  more  soluble  than  any  of  the  minerals  we 
have  studied.  One  pound  of  it  will  dissolve  in  400  pounds, 
or  about  400  pints  of  water.  It  is  hydrated  calcium  sul- 
phate. What  important  essential  element  not  present  in 
the  previous  minerals  is  supplied  by  selenite? 

Apatite  is  of  various  colors,  but  most  commonly  gray. 
It  is  heavier  than  the  minerals  thus  far  studied,  having  a 
specific  gravity  of  3.2.  In  hardness  it  ranks  next  to  feld- 
spar. It  is  more  soluble  than  quartz,  but  less  soluble  than 
mica.  Its  crystals  are  scattered  through  the  older  rocks. 
In  places  it  occurs  in  masses  and  is  quarried  for  fertilizer 
production.    Apatite    consists    of    tri-calcium    phosphate 


200  CHEMISTRY  OF  THE  FARM  AND  HOME 

crystallized  with  either  calcium  chloride  or  calcium  fluo- 
ride. What  do  you  judge  to  be  the  chief  value  of  this 
mineral  to  the  soil? 

Calcite,  a  form  of  calcium  carbonate,  is  a  white  mineral 
occurring  in  crystals  about  three  times  as  hard  as  talc,  but 
only  half  as  hard  as  feldspar.  Limestone,  chalk  and  marble 
are  of  the  same  composition  as  calcite.  The  first  two  rep- 
resent the  accumulated  shells  of  various  shellfish.  Marble 
has  been  formed  from  such  deposits  by  the  action  of  pres- 
sure and  heat.  Calcite  is  only  a  little  more  soluble  in  water 
than  is  feldspar.  If  water  is  saturated  with  carbon  dioxide, 
however,  it  can  dissolve  thirty  times  as  much  calcite  as 
when  pure.  If  the  carbon  dioxide  escapes  from  the  water, 
most  of  the  calcite  separates  from  solution.  This  is  the 
way  in  which  limestone  had  been  removed  from  some 
places  and  built  up  in  others  to  form  fantastic  caves,  such 
as  the  famous  Mammoth  Cave  of  Kentucky.  This  process 
is  common  on  a  small  scale  in  fertile  soils.  On  account  of 
the  weakness  of  carbonic  acid  there  is  a  great  tendency  for 
calcite  to  react  with  any  acids  which  may  get  into  the  soil. 
What  change  do  you  think  occurs  in  these  reactions? 

Dolomite,  is  a  mineral  consisting  of  a  mixture  of  cal- 
cium and  magnesium  carbonates.  It  is  estimated  that  calcite 
and  dolomite  together  form  about  1  per  cent  of  the  earth's 
solid  crust. 

Limonite  is  a  hydrated  oxide  of  iron.  It  does  not  occur 
in  crystals,  but  in  irregular  lumps  of  a  brownish  color.  It 
has  the  same  composition  as  iron  rust.  The  mineral  is 
hard,  has  a  specific  gravity  of  3.6  to  4.0  and  is  brown  to 
yellow  in  color.  It  forms  the  chief  coloring  matter  of  soils. 
Has  it  any  food  value  to  plants? 

The  various  soil  minerals  have  been  more  or  less  broken 
away  in  fragments  from  the  original  parent  rocks  during 
past  ages.  These  fragments  have  also  been  cemented 
together  in  some  cases  to  form  newer  rocks.    Prominent 


THE  SOIL 


201 


among   these   rocks   are   the   sandstones.     The   cementing 
mineral  may  be  calcite,  kaoUnite,  hmonite  or  quartz. 

Humus.  Organic  matter,  or  the  material  called  humus, 
is  as  essential  to  the  fertile  soil  as  any  of  the  minerals. 
This  dark,  spongy  material  results  from  the  partial  decay 
and  oxidation  of  the  mixture  of  organic  compounds  added 
to  the  soil  minerals  by  plant  remains,  farni  manure  and 

similar  materials.  Surely 
you  must  have  had  an 
opportunity  to  observe 
the  surface  of  vertical 
cuts  in  the  soil  like 
those  made  for  ditches. 
Have  you  noticed  any 
difference  in  color  be- 
tween the  surface  soil 
and  that  raised  from  a 
depth  of  a  foot  or  more? 
Sometimes  one  can  find 
a  quite  sharp  line  of  sep- 
aration where  the  dark 
soil  is  replaced  by  lighter 
colored  soil.  The  Hghter 
colored  soil  is  lacking  in  humus.  Organic  matter  has  not 
reached  a  depth  of  more  than  a  few  inches  in  some  soils. 

Much  attention  has  been  given  by  chemists  in  recent 
years  to  the  study  of  humus.  Many  waxes,  resins,  organic 
acids,  carbohydrates  and  nitrogenous  compounds  resulting 
from  the  original  organic  matter  and  its  decomposition 
have  been  separated  from  it.  The  most  important  phy- 
sical properities  of  humus  are  its  gumminess  and  its  power 
to  absorb  water.  By  the  former  property  it  binds  the 
mineral  particles  together.  The  most  important  chemical 
properties  of  humus  are  its  affinity  for  oxygen  and  the  pres- 
ence of  nitrogen  in  its  compounds.      Products  formed  in 


Figure  58.  A  Limestone  Cave.  The  flang- 
ing stalactites  and  the  standing  stalag- 
mites consist  of  calcium  carbonate 
deposited  from  solution  in  water  as  the 
carbon  dioxide  escapes. 


202  CHEMISTRY  OF  THE  FARM  AND  HOME 

its  oxidation  help  to  dissolve  soil  minerals  for  plants.  As  a 
source  of  nitrogen  for  plants  it  is  of  very  great  importance. 
For  this  reason  clover  and  other  legumes,  which  contain 
more  nitrogen  than  grain  and  root  crops,  make  valuable 
humus.  Humus  has  also  important  biological  properties. 
Chief  of  these  is  the  support  and  nourishment  it  provides 
for  bacteria  and  other  organisms  which  increase  the  fer- 
tility of  the  soil.  It  is  a  material  fairly  throbbing  with 
life  processes  and  ceaselessly  astir  with  chemical  reactions. 
As  a  result  of  these  conditions  organic  matter  loses  its  in- 
dependence as  soon  as  it  is  tilled  into  the  soil,  the  products 
of  its  decay  combining  more  or  less  with  the  minerals  to 
form  humus. 

Pulverizing  Agents.  Before  the  chemical  changes  which 
make  fertile  soils  can  proceed  rapidly  the  coarse  rock  frag- 
ments must  be  pulverized.  This  process  has  been  accom- 
plished in  past  ages  and  is  proceeding  at  present  by  the 
action  of  several  physical  agents.  The  glaciers  accom- 
plished a  great  deal  of  this  work  in  the  northern  part  of  our 
own  country.  Grinding  rock  upon  rock  with  enormous 
pressures  as  they  moved  down  across  the  continent,  they 
left  large  areas  of  pulverized  soil  minerals  either  spread  or 
piled  in  their  wakes  as  they  melted  back.  The  soils  so 
formed  are  among  the  most  fertile. 

Ice  is  still  an  active  agent  in  soil  formation  on  a  smaller 
scale.  When  the  earth  is  moist  the  cracks  and  crevices  in 
stones  and  rocks  become  filled  with  water.  In  freezing 
weather  this  water  is  changed  to  ice  right  in  the  crevices. 
Now,  from  your  study  of  physics  what  change  of  volume  do 
you  know  to  occur  when  water  freezes?  The  force  pro- 
duced in  this  way  is  very  great  and  splits  rocks  to  fragments. 

Rapidly  running  water  and  winds  of  high  velocity  also 
contribute  gradually  to  the  making  of  soil.  The  moving 
water  grinds  stones  upon  one  another  or  along  the  bed  of 
the  stream,  and  the  wind  hurls  sand  particles  against  cliffs 


THE  SOIL 


203 


and  rocks.  In  these  ways  fine  material  is  slowly  ground 
away  from  the  surface  of  rocks.  This  material  may  be 
carried  along  by  the  water  or  wind  and  deposited  to  form 
soil  in  some  new  place. 

Plants  and  animals  also  help  in  the  disintegration  of 
rocks.  The  roots  of  trees  are  especially  effective.  They 
often  penetrate  cracks  in  rocks  and  then  split  them  apart 
by  their  great  power  of  growth  as  they  enlarge.  Earth- 
worms are  especially  active  in  stirring  the  soil  particles 
about  and  ants  accumulate  the  finer  soil  particles  to  form 
their  homes. 

Temperature  causes  changes  also,  because  it  produces  an 
unequal  expansion  and  contraction  of  different  minerals, 
sets  up  powerful  stresses  in  rocks  and  causes  them  to  go  to 
pieces. 

Let  us  turn  for  a  moment  to  some  principles  met  in  the 
chemical  laboratory.  Which  will  dissolve  quickest,  a  quan- 
tity of  coarse  rock  salt  or  the  same  quantity  of  salt  pulver- 
ized to  a  fine  powder?     How  would  you  expect  the  same 


Figure  59. 


The  production  of  scil  from  limestone  rock  by  physical  and  chem- 
ical forces.      Limestone  makes  fertile  soil. 
Courtesy  of  W,  O.  Hotchkiss,  Wis.  Geol.  Survey 


204      CHEMISTRY  OF  THE  FARM  AND  HOME 

difference  of  condition  to  affect  the  rate  of  decay  of  organic 
matter?  The  same  principles  apply  to  the  soil  minerals, 
and  to  humus.  That  is  why  the  physical  changes  which 
disintegrate  rocks  are  so  important  in  the  making  of  soil. 
The  chemical  changes  which  make  food  materials  available 
to  plants  proceed  more  rapidly  in  fine  than  in  coarse  mineral 
particles. 

The  texture  of  the  soil  is  very  important  in  the  growth 
of  crops.  This  is  because  the  texture  controls  to  a  great 
extent  the  power  of  the  soil  to  hold  water,  its  content  of 
air  and  the  rate  at  which  the  minerals  dissolve.  Would 
you  expect  the  more  oxygen  to  be  at  hand  for  the  oxidation 
of  humus  material  in  coarse  sandy  soil  or  in  compact  clay 
soil?  Do  you  not  see  that  here  is  a  relation  important  in 
the  fertility  of  the  soil?  A  soil  consisting  of  fine  particles 
will  hold  more  water  than  one  of  coarse  sand.  In  the 
finer  material  there  is  more  total  surface  on  the  soil  grains 
than  in  the  sand.  For  example,  one  cubic  inch  of  space 
will  contain  1,000,000  spheres  each  1-10  inch  in  diameter  the 
total  surface  of  which  will  be  314.2  square  inches.  Let  the 
diameter  of  each  sphere  be  1-1,000  of  an  inch,  however,  and 
the  cubic  inch  will  hold  1,000,000,000  of  such  spheres  the 
total  surface  of  which  will  be  3,142  square  inches.  The 
particles  of  a  fertile  soil  are  covered  with  a  film  of  water 
attracted  to  them  and  held  by  a  physical  force  called  ab- 
sorption. From  what  has  just  been  said  would  you  expect 
the  fine  or  the  coarse  soil  to  hold  the  more  water?  Further- 
more, the  finer  soil  particles  make  much  closer  contact 
than  the  coarser  ones.  The  strength  of  the  films  of  water 
is  thus  increased,  so  that  the  whole  mass  of  water  in  the 
soil  moves  rapidly  to  the  surface  to  replace  that  removed 
by  plants  or  lost  by  evaporation.  The  rise  of  water  in 
this  manner,  as  in  tubes  of  very  small  bore,  is  called  capil- 
larity? Do  you  see  herein  any  explanation  of  the  bene- 
ficial effects  of  frequent  shallow  tillage  during  dry  seasons 


THE  SOIL 


205 


and  in  regions  where  dry  farming  must  be  practiced?  There 
is  another  advantage  in  fineness  of  the  soil  minerals.  By 
the  more  thorough  contact  with  the  soil  water  more  plant 
food  material  is  dissolved  for  the  plant  than  in  coarse  soils. 
The  physical  properties  of  the  soil,  such  as  its  power  to 
absorb  water  and  heat,  depend  directly  upon  the  proper- 
ties of  humus  and  the  minerals.     They  also  depend  upon 

the  proportion 
in  which  these 
different  constit- 
uents are  pres- 
ent. If  we  were 
to  cut  cubes  of 
equal  size  from 
dried  sand,  clay 
and  peat  w  e 
would  find  the 
peat  about  one 
third  heavier 
than  water,  while 
the  sand  and 
clay  would  each 
weigh  about 
twice  as  much 
as  the  peat. 
These  differences 
are  directly  due  to  the  differences  of  specific  gravity  be- 
tween the  chief  constituents  of  the  three  soils,  which  are 
quartz,  kaolinite  and  humus  respectively. 

If  we  were  to  immerse  the  bottoms  of  these  cubes  of 
dry  soil  in  water  and  let  them  soak  up  the  liquid  until  they 
stopped  gaining  weight  we  would  find  important  differ- 
ences. In  this  volume  of  one  cubic  foot,  which  is  about 
48  pints,  the  sand  would  take  up  22  pints  of  water.  The 
clay  would  take  up  33  pints  and  the  peat  40  pints.     So  we 


Figure  60.  The  power  of  soils  to  absorb  water.  At  the 
left  is  a  cylinder  of  dry  peat.  The  next  cylinder  con- 
tains the  amount  of  water  it  can  absorb.  The  third 
cyhnder  contains  the  amount  of  water  that  dry  clay 
of  the  same  volume  as  the  peat  can  absorb.  Tiie 
fourth  cylinder  shows  the  amount  of  water  which 
medium  fine  sand  can  hold. 


206 


CHEMISTRY  OF  THE  FARM  AND  HOME 


see  that  the  clay  and  peat  soils  hold  water  far  better  than 
sand.  But  this  is  not  all  in  their  favor,  for  they  also  re- 
tain the  water  more  strongly  than  sand.  In  this  way  they 
withhold  it  from  the  plant.  Plants  will,  therefore,  wilt 
upon  the  clay  and  peat,  while  they  still  contain  about  9 
pints  of  water  per  cubic  foot.  The  water  content  of  sand, 
on  the  other  hand,  will  fall  to  about  3  pints  per  cubic  foot 
before  plants  will  wilt.     Given  a  sufficient  supply  of  plant 


Figure  61.     Laying  tile  drains  to  warm  and  ventilate  the  soil. 

food  material  in  them,  which  of  these  types  of  soil  would 
you  select  in  a  region  of  low  rainfall?  Clay  soils  often 
take  on,  when  wet,  the  * 'puddled' '  condition  mentioned  in 
discussing  kaolinite.  They  can  be  made  porous  by  adding 
lime.  This  process  of  rendering  soils  porous  is  called  floccu- 
lation. 

The  heat  absorbing  power  of  the  soil  depends  chiefly 
upon  its  water  content.  This  is  due  to  the  high  specific 
heat  of  water.  As  you  may  know,  it  is  taken  as  a  standard 
for  measuring  heat  absorption  in  physics  and  given  the 
value  one.     For  equal  volumes  of  the  materials  sand  ab- 


'       THE  SOIL  207 

sorbs  only  one  half  as  much  heat  as  water,  and  clay  and 
humus  less  than  0.6  as  much.  Is  any  further  evidence 
necessary  that  the  amount  of  water  present  largely  deter- 
mines the  temperature  of  a  soil?  Wet  soils  are  notoriously 
*'cold"  and  late  in  producing  crops.  Their  only  cure  is 
drainage.  This  not  only  warms  the  soil  but  admits  air, 
which  replaces  unfavorable  by  favorable  bacterial  proc- 
esses and  chemical  changes.  Can  you  not  suggest  reasons 
for  the  high  favor  in  which  sandy  soils  stand  among  growers 
of  early  truck  crops? 

The  chemical  properties  of  soils  depend  upon  the  kinds 
of  compounds  and  reactions  most  common  in  them.  These 
reactions  are  most  rapid  and  extensive  in  the  humus.  Oxi- 
dation is  the  most  important  of  them.  It  may  be  either 
complete  or  incomplete,  depending  upon  the  supply  of 
oxygen  in  the  soil.  When  it  is  complete,  the  elements  of 
the  organic  compounds  in  the  humus  forming  material  are 
set  free, — carbon  as  carbon  dioxide,  hydrogen  as  water, 
nitrogen  as  nitric  acid,  sulphur  as  sulphuric  acid,  and  so  on. 
As  a  matter  of  fact,  though,  parts  of  some  of  the  organic 
compounds  resist  oxidation  for  a  long  time.  These  form  a 
large  share  of  the  dark,  spongy  material  called  humus.  All 
the  products  of  oxidation  are  extremely  useful.  The  car- 
bon dioxide  may  escape  to  the  air  and  become  the  source 
of  carbon  for  plants.  It  may  also  remain  dissolved  in  the 
soil  water,  greatly  increasing  its  power  to  dissolve  minerals. 
We  have  already  considered  its  action  upon  limestone. 
Selenite,  apatite  and  feldspar  are  two  to  three  times  as 
soluble  in  carbonated  water  as  in  pure  water.  By  the  ac- 
tion of  carbon  dioxide  in  solution  upon  feldspar  potassium 
is  made  soluble  as  the  carbonate,  and  kaolinite  is  left  as  a 
residue.  By  further  long  continued  action  the  aluminium  is 
removed  from  this  mineral  and  only  quartz  remains.  In  this 
way  clay  and  sandy  soil  are  formed  successively  from  feld- 
spar-bearing rocks,  such  as  the  granites.     As  the  potassium 


208 


CHEMISTRY  OF  THE  FARM  AND  HOME 


is  gradually  removed  the  soil  becomes  poorer,  until  pure, 
infertile  sand  is  reached.  Of  course,  it  takes  hundreds  of 
thousands  of  years  for  a  granite  rock  to  pass  through  these 
changes.  The  most  important  fact  is  that  useful  elements 
are  ceaselessly  being  prepared  in  this  way  for  the  feeding  of 
plants. 

The  oxidation  of  organic  matter  in  the  soil  is  caused 
chiefly  by  bacteria.     These  organisms  are  equipped  with  a 


Figure  62.     Irrigating  crops  in  the  dry  climate  of  Utah. 

whole  arsenal  of  enzymes  for  this  attack.  Both  the  life  of 
the  bacteria  and  the  chemical  changes  they  produce  are 
favored  by  the  warm  temperatures  of  the  summer  months. 
Hence  their  useful  products  are  formed  in  the  soil  at  just 
the  season  when  the  growing  plants  need  them. 

Nitrification  is  the  particular  oxidation  process  by  which 
nitrogen  is  changed  to  nitric  acid.  Special  kinds  of  bacteria 
cause  it.  It  is  especially  important,  because  it  is  the  only 
source  of  nitrogen  for  all  plants  but  the  legumes.  Further- 
more,  perhaps  no   other   chemical   element,   even   carbon 


THE  SOIL  209 

itself,  is  more  necessary  to  the  chemical  processes  of  life 
than  is  nitrogen.  If  the  nitric  acid  formed  by  nitrification 
were  to  accumulate  in  the  soil,  it  would  soon  become  in- 
jurious to  plants;  for,  as  a  rule,  they  cannot  endure  much 
acidity  of  the  soil  water.  This  condition  is  prevented, 
however,  by  some  of  the  soil  minerals.  Review  the  text 
about  minerals  and  learn  which  is  especially  useful  in  neu- 
tralizing acids.  Sulphur,  nitrogen  and  phosphorus  freed 
from  humus  by  oxidation  thus  enter  the  plant  as  constit- 
uents of  sulphates,  nitrates  and  phosphates  of  potassium 
and  calcium  or  other  metals. 

When  air  is  pretty  much  excluded  from  the  soil,  as 
where  much  water  is  present,  oxidation  is  incomplete.  In 
such  cases  organic  acids,  which  are  products  of  partial  oxi- 
dation of  other  organic  compounds,  may  be  formed.  What 
would  then  happen,  if  calcite  were  also  present?  In  such 
cases,  also,  reduction  may  even  go  on.  That  is,  carbon, 
unsatisfied  in  its  affinity  for  oxygen,  may  remove  this  ele- 
ment entirely  from  nitrogen.  The  latter  element,  at  great 
loss  to  the  fertility  of  the  soil,  will  then  escape  into  the  air 
as  a  free  gas.  All  the  energy  expended  by  legume  crops 
in  obtaining  it  will  thus  be  lost.  This  particular  process, 
called  denitrification,  is  due  to  special  kinds  of  bacteria. 
Knowing  that  the  presence  of  too  much  water  and  too  little 
air  is  the  cause,  how  would  you  treat  the  soil  to  avoid  it? 

Retention  of  Fertilizers  by  Soil  Minerals.  The  minerals 
of  the  soil  also  take  part  in  its  chemical  reactions.  We 
have  seen  how  they  combine  with  products  formed  in  the 
oxidation  of  humus.  Perhaps  the  next  most  important 
way  in  which  they  react  is  in  "fixing' '  soluble  fertilizer  com- 
pounds. By  this  is  meant  the  rendering  of  soluble  fertilizing 
elements  iusoluble,  such  as  by  forming  precipitates  with  them. 

Calcite  and  limonite  react  with  acid  phosphate  when  it 
is  applied  to  the  soil.  They  cause  the  precipitation  of  phos- 
phoric acid  from  the  soluble  form  as  insoluble  phosphates 

14— 


210  CHEMISTRY  OF  THE  FARM  AND  HOME 

of  calcium  or  iron.  The  loss  of  phosphorus  by  leaching 
out  of  the  surface  soil  is  thus  prevented.  At  the  same 
time,  the  new  phosphates  formed  are  so  finely  divided 
as  to  dissolve  in  the  carbonated  soil  water  for  the  use  of 
plants. 

By  double  decomposition  potassium  is  taken  from  its  salts 
by  some  of  the  silicon  minerals  and  some  other  metal  is  set 
free  in  its  place.  The  zeolites  possess  this  power  to  the 
greatest  extent.  They  resemble  the  micas  in  composition 
and  are  believed  to  have  been  reformed  from  older  rocks. 
They  contain  water;  and  to  this  their  reactiveness  is  at- 
tributed. Zeolites  are  abundant  in  the  dark  trap  rock 
which  forms  the  famous  Palisades  of  the  Hudson. 

Alkali  soils  are  a  special  difficulty  to  farmers  of  some 
regions.  So  much  of  various  salts  accumulates  in  the 
surface  soil  of  these  regions  that  they  become  poisonous  to 
most  plants.  Alkali  soils  are  common  in  the  western  part 
of  the  United  States.  The  salts  which  they  contain  may 
have  been  left  behind  in  the  evaporation  of  undrained 
lakes  like  the  Great  Salt  Lake.  Sodium  chloride,  sodium 
sulphate  and  sodium  carbonate  are  the  most  common  salts 
of  alkali  soils.  Because  the  sodium  carbonate  dissolves 
some  of  the  humus  and  so  darkens  the  surface  of  the  soil, 
it  is  called  ''black  alkali."  It  is  more  injurious  to  crops 
than  the  other  salts.  Gypsum  improves  ''black  alkali"  by 
reacting  with  it  to  form  the  less  poisonous  sodium  sulphate 
and  calcium  carbonate.  The  best  treatment  for  "white 
alkali,"  so  called  from  the  white  crust  of  sodium  sulphate 
and  other  salts,  is  irrigation  combined  with  drainage. 
This  washes  the  salts  from  the  soil.  In  dry  climates  it  is 
the  practice  to  till  the  soil  frequently  so  as  to  check  eva- 
poration and  the  rise  of  alkali  salts  to  the  surface  by  capil- 
larity. The  following  figures  show  great  differences  between 
a  plant  native  to  jegions  of  alkali  soils  and  some  common 
crops. 


THE  SOIL 


211 


Table  VII. 

Greatest  amounts  of  salts  which  can  be 
injury  to  the  plants  named 

present  without 

Sodium 
Carbonate 

Sodium 
Chloride 

Sodium 
Sulphate 

Peach 

700* 
1,500 
2,400 
18,600 

1,000 

1,200 

5,800 

12,500 

9,600 

15,100 

102,500 

125,600 

Wheat 

Alfalfa 

Salt  Bush 

♦Values  are  pounds  of  salt  in  the  four  surface  feet  of  soil  per  acre. 

Analysis  of  the  soil  to  determine  its  fertility  value  is 
carried  out  in  the  laboratory  in  two  ways.     One  method, 

mechanical  analysis,  determines 
the  proportion  of  particles  of  dif- 
ferent sizes.  The  soil  grains  are 
graded  from  clay  through  silt  and 
fine  to  coarse  sand  up  to  fine 
gravel.  This  division  can  be  made 
by  the  different  rates  at  which  the 
larger  and  smaller  particles  sink 
in  water.  It  is  a  measure  of  tex- 
ture. The  other  method,  chem- 
ical analysis,  determines  either 
the  total  amounts  of  the  essen- 
tial elements  present  or  the 
amounts  soluble  in  some  solvent. 
Figure  G3.  John  B.  Lawes,  1814-  It  is  wcll  for  the  farmer  to  know 
RoXmstTd^  Expe°rfmenf  s^ta-  the  total  store  of  plant  food  in  his 

be^'q^ueathed    To   the    people    of    Soils.       That    kuOwlcdgC,     hoWCVer, 

L""Sso?riroTTn\"rrtfon  docs  not  inform  him  how  much 

about  the  food  needs  of  crops.   f^^^  ^^^     ^^.^pg  ^^^      ^^^  rj.^^ 

part  which  the  crops  can  get  is  called  ' 'available"  plant  food. 
Water  and  acids  of  various  strengths  have  been  used  to  ex- 
tract it  from  the  soil.  None  of  these  agents  is  very  satisfac- 
tory, however.  They  cannot  be  made  to  duplicate  at  one 
time  the  varied  combined  action  of  plants,  bacteria  and 


212  CHEMISTRY  OF  THE  FARM  AND  HOME 

the  soil  solution  upon  the  stores  of  plant  food  materials 
in  the  soil.  They  are  useful  for  comparing  soils  with  one 
another,  but  none  can  approach  the  accuracy  of  using  the 
growing  plant  itself  as  a  measure  of  availability.  So  we  find 
that  the  study  of  the  plant  and  of  the  soil  are  inseparably 
dependent  upon  each  other.  A  fertile  soil  is,  indeed,  the 
necessary  foundation  for  prosperity  in  agriculture  and  the 
welfare  of  man. 

SUMMARY 

In  the  process  of  cooling  from  a  very  hot  gaseous  state  the  chem- 
ical elements  which  formed  the  earth  united  to  form  water  and  minerals. 
Some  of  the  latter  have  been  changed  in  composition  during  past  ages 
and  some  of  them  are  very  complex  in  chemical  structure.  With  the 
coming  of  living  things  which  attached  themselves  to  the  rocks  the 
destruction  of  the  latter  and  the  formation  of  fertile  soils  went  on 
rapidly.  The  soil  is  not  a  fixed  portion  of  these  materials,  but  is  a 
state  in  which  they  are  continuously  being  destroyed  and  renewed. 

The  formation  of  fertile  soil  requires  the  breaking  of  rocks  into 
small  particles.  In  past  ages  the  glaciers  did  much  of  this  work. 
Other  forces,  which  are  still  active  from  season  to  season,  have  been 
the  expansion  of  freezing  water,  stresses  in  the  rock  due  to  temperature 
changes  and  the  grinding  action  of  running  water  and  sand-laden  wind. 
The  destruction  of  organic  matter,  which  is  of  importance  equal  to 
the  breaking  of  rocks,  is  chiefly  due  to  oxidation,  caused  by  bacteria 
and  other  hving  things  of  the  soil.  (The  proper  favoring  of  those  forces 
which  make  the  rock  and  organic  materials  useful  requires  no  mean 
degree  of  skill  in  the  farmer.) 

Most  rocks  are  cemented  mixtures  of  different  minerals.  The 
greater  part  of  these  minerals  is  formed  by  silicic  acid  and  insoluble, 
resistant  salts  which  it  forms  with  aluminium,  as  well  as  with  potassium, 
magnesium  and  other  basic  elements  essential  to  plants.  In  some  of 
the  simpler  soil  minerals  essential  ac  id  elements  are  present,  as  sulphur 
in  selenite  and  phosphorus  in  apatite. 

Humus,  present  only  in  the  surface  soil,  results  from  the  partial 
oxidation  of  plant  tissues,  farm  manure  and  similar  organic  matter. 
It  binds  the  mineral  particles  together,  aids  in  dissolving  them  for  plants 
and  supplies  nitrogen  to  the  soil.  Proper  warmth  and  airing  of  the 
soil  are  necessary  to  the  greatest  usefulness  of  humus. 

The  chief  physical  properties  of  the  soil  are  its  power  to  absorb 
water  and  heat.     Fineness  of  the  mineral  particles  and  presence  of  much 


THE  SOIL  213 

humus  increases  the  absorption  of  water.  The  power  of  the  soil  to 
absorb  heat  is  controlled  by  the  amount  of  water  present.  Too  much 
water,  by  absorbing  heat,  makes  the  soil  cold  and  should  be  avoided 
by  tile  drainage. 

The  chemical  properties  of  the  soil  depend  upon  the  composition 
and  chemical  reactions  of  the  minerals  and  humus.  Oxidation  of  the 
humus  is  very  important  in  this  respect.  When  it  is  complete,  useful 
products  such  as  carbon  dioxide,  nitric  acid,  sulphuric  acid  and  so  on 
are  formed.  Calcite  favors  the  process  by  neutralizing  the  acids  as. 
they  are  formed,  thus  preventing  injury  to  the  bacteria  or  plants. 
The  particular  process  of  oxidizing  the  nitrogen  of  humus  is  called 
nitrification.  In  poorly  drained  soils,  lacking  oxygen,  organic  acids 
and  free  nitrogen  are  produced  from  the  humus.  Other  minerals  than 
calcite  take  part  in  chemical  reactions  of  the  soil,  especially  with  some 
soluble  fertilizers.  Certain  sihcates,  the  zeolites,  combine  with  potas- 
sium ;  and  calcite  and  limonite  produce  insoluble  phosphates.  Loss  by 
leaching  is  thus  prevented.  Alkali  soils  present  special  injurious  con- 
ditions whose  only  complete  remedy  is  the  combining  of  irrigation 
with  drainage. 

Mechanical  and  chemical  methods  for  analyzing  the  soil  are 
valuable,  especially  for  comparing  different  soils.  The  growth  of  plants 
upon  the  soil  is  still  the  only  method,  however,  by  which  fertility  can 
be  measured  accurately. 

QUESTIONS 

1.  Name  soil  minerals  which  contain  the  following  elements: 
potassium,    calcium,    magnesium,    iron,    sulphur,    phosphorus. 

2.  How  is  humus  formed? 

3.  What  are  its  important  chemical  and  physical  properties? 

4.  In  what  way  does  fineness  promote  the  value  of  soil  minerals? 

5.  How  do  water  and  temperature  act  to  pulverize  the  minerals? 

6.  Which  type  of  soil  has  the  greatest  water-holding  power? 

7.  What  is  the  chief  cause  of  coldness  in  soils?  What  is  the 
remedy? 

8.  What  causes  the  oxidation  of  organic  matter  in  the  soil? 
Why  is  the  change  important? 

9.  What  is  nitrification?     Denitrification? 

10.  What  is  the  composition  of  zeohtes?  Why  are  they  im- 
portant in  soils? 

11.  Why  are  calcite  and  limonite  important  in  soils? 

12.  What  is  the  cause  of  alkali  soils?     Of  black  alkali? 

13.  How  can  these  soil  troubles  be  treated? 

14.  What  is  the  mechanical  method  of  soil  analysis?  What 
property  does  it  measure? 

15.  What  is  meant  by  the  term  "available"  when  applied  to 
plant  food  of  the  soil? 


CHAPTER  VIII 
FERTILIZERS 

The  earlier  meaning  of  manure  included  anything 
which  rendered  the  soil  more  productive.  Even  tillage 
was  called  by  some  a  manuring  of  the  land.  A  true  under- 
standing of  the  fundamental  principles  of  manuring  was 
made  possible  by  the  aid  of  chemistry.  Justus  von  Liebig 
became  the  central  figure  in  the  study  of  this  particular  phase 
of  chemistry.  Other  noted  investigators  were  Lawes  and 
Gilbert  who  established  the  Rothamsted  Experiment  Farm, 
the  first   step   in   systematic  agricultural  experimentation. 

Classes.  There  are  numerous  kinds  of  manures  and 
fertilizers  some  of  which  have  several  functions  or  uses. 
They  may  be,  however,  roughly  divided  into  classes,  such  as 
(1)  commercial  fertilizers,  (2)  farm  manures,  (3)  green 
manures,  and  (4)  soil  amendments.  This  chapter  will 
be  limited  to  commercial  fertiUzers  and  soil  amendments. 

Commercial  Fertilizers.  These  substances  are  quite 
varied  in  character  depending  upon  their  source  and  their 
chemical  composition.  Their  chief  function  is  to  add  plant 
nutrients  to  the  soil,  though  there  may  be  other  bene- 
ficial effects  produced  by  certain  fertilizers.  A  fertilizer 
may  be  useful  on  account  of  the  presence  of  one  or  more 
plant  nutrients.  The  composition  and  solubility  of  these 
ingredients  directly  affect  the  value  of  the  fertilizer. 

As  already  indicated,  there  are  ten  chemical  elements 
which  are  required  for  plant  life.  Commonly  only  three 
of  these  are  likely  to  be  deficient  in  soils  and  must  then  be 
supplied  to  the  plant  for  its  proper  growth.  I^et  us  now 
discuss  the  materials  grouped  under  each  of  these  elements. 

Fertilizers  Used  for  Their  Nitrogen.  Nitrogen  is 
probably   the   most    important    constituent    of   fertilizers. 

214 


FERTILIZERS  215 

In  the  first  place  it  is  quite  likely  to  be  deficient  in  soils. 
Then  its  availability  to  crops  varies  greatly  depending  upon 
the  kind  of  material  which  carries  it.  Finally,  it  is  the  most 
expensive  ingredient  of  fertilizers.  The  nitrogen  of  commer- 
cial fertilizers  may  be  in  the  form  of  a  soluble  inorganic 
salt  or  combined  in  organic  matter.  The  inorganic  com- 
pounds are  readily  soluble  and  available  to  plants,  while 
thfe  organic  forms  must  pass  through  the  various  processes 
leading  to  nitrification  before  the  plant  can  use  them.  It 
is  necessary  to  know,  therefore,  the  character  of  the  com- 
pound or  material  which  contains  the  nitrogen. 

The  principal  inorganic  nitrogen  fertilizers  are  sodium 
nitrate,  ammonium  sulphate,  calcium  nitrate,  calcium 
cyanamide  and  ammonium  nitrate.  Other  materials  are 
sometimes  used,  such  as  potassium  nitrate.  One  of  these, 
sodium  nitrate,  is  a  natural  product;  another,  ammonium 
sulphate,  is  a  by-product  of  the  manufacture  of  illuminat- 
ing gas;  the  others,  calcium  nitrate,  calcium  cyanamide 
and  ammonium  nitrate  are  manufactured  from  atmospheric 
nitrogen  especially  for  use  as  fertilizers  and  for  other  commer- 
cial purposes.  What,  for  example,  is  an  important  use  of 
nitric   acid?    of   ammonia? 

Sodium  Nitrate.  This  salt  occurs  in  the  crude  condition 
in  northern  Chile.  It  is  believed  that  the  compound  ac- 
cumulated there  from  a  combination  of  circumstances, 
the  action  of  soil  organisms  through  a  very  long  period,  the 
freedom  of  the  region  from  rains,  etc.  The  crude  salt  is 
dug  from  beneath  an  overlying  layer  of  earth,  and  is  puri- 
fied by  dissolving  in  water  and  by  crystallization.  As 
marketed,  it  contains  about  96%  sodium  nitrate,  equal  to 
about  16%  nitrogen,  2%  water,  and  small  amounts  of  im- 
purities, such  as  chlorides,  sulphates  and  insoluble  matter. 

Sodium  nitrate  is  very  soluble  in  water;  in  fact  it  readily 
absorbs  moisture  from  the  atmosphere.  On  account  of  this 
fact  it  is  easily  available  in  the  soil  and  is  the  most  active 


216  CHEMISTRY  OF  THE  FARM  AND  HOME 

form  of  a  nitrogenous  fertilizer.  It  is  used  largely  by  mar- 
ket gardeners  and  wherever  quick  growth  is  desired.  On 
meadow  land  and  small  grains  it  stimulates  growth  before 
nitrification  makes  the  soil  nitrogen  available. 

Sodium  nitrate  is  not  easily  absorbed  by  the  soil  in  large 
quaxitities  and  is  easily  lost  in  the  drainage  water.  Would 
you  apply  this  fertilizer,  then,  where  there  were  no  crops 
upon  the  soil?  Would  you  advise  large  or  small  applica- 
tions even  if  there  are  growing  crops?  The  long  continued 
use  of  sodium  nitrate  results  in  injury  to  the  soil.  On 
account  of  the  fact  that  the  nitrogen  is  used  by  the  plant 
much  more  abundantly  than  the  sodium,  the  latter  accum- 
ulates in  the  form  of  sodium  salts,  particularly  sodium 
carbonate.  This  compound  chemically  is  a  mild  alkali  (do 
you  recall  some  of  its  uses?)  and  produces  a  defloccu- 
lating  action,  breaking  down  the  soil  particles  and  com- 
pacting and  injuring  the  soil  structure. 

Ammonium  Sulphate.  This  compound  is  a  by-pro- 
duct in  the  manufacture  of  illuminating  gas.  How  is  it 
prepared?  Why  is  the  ammonia  separated  from  the  illum- 
inating gas?  Commercial  ammonium  sulphate  contains 
about  20%  nitrogen.  It  is  a  more  concentrated  nitrogenous 
fertilizer  than  sodium  nitrate,  having  60  to  80  pounds  more 
nitrogen  to  the  ton.  Which  of  these  two  fertilizers  would 
have  the  advantage  of  cheaper  freight  rates  per  pound  of 
nitrogen  supplied?  It  does  not  have  as  quick  an  effect 
upon  crop  growth  as  Chile  saltpetre,  but  it  is  less  quickly 
removed  by  drainage  water,  as  the  ammonium  salts  are 
more  readily  absorbed  and  retained  by  the  soil.  The  nitro- 
gen in  the  nitrate  and  ammonium  sulphate  cost  about  the 
same  per  pound.     Which  fertilizer  costs  the  more  per  ton? 

The  long  continued  use  of  ammonium  sulphate  on  soils 
affects  the  condition  of  the  latter  and  produces  results  that 
are  unfavorable  for  crop  growth.  These  results  are  due  to 
the  fact  that  the  ammonium  radicle  is  utilized  more  rapidly 


FERTILIZERS  217 

than  the  sulphate  radicle  and  the  latter  consequently  accum- 
ulates in  the  soil,  giving  rise  to  so-called  acid  soils. 

Nitrogen  from  the  Air.  The  supply  of  nitrogen  in  the 
soil  is  limited.  Though  there  are  certain  tendencies  of 
nature  to  constantly  restock  the  soil  with  this  constituent, 
yet  there  are  other  tendencies  for  the  supply  to  be  contin- 
ually depleted.  The  necessity  for  applying  nitrogenous 
fertilizers  in  order  to  stimulate  crop  growth  has  been  recog- 
nized for  a  long  time.  The  amount  of  available  nitrogen, 
though,  is  yearly  becoming  smaller  and  it  will  be  necessary, 
when  the  supply  of  Chile  saltpetre  is  exhausted,  to  secure 
another  source  of  nitrogen  for  this  purpose.  Where  is  the 
most  abundant  supply  of  this  element  in  nature?  Where 
will  man  find  the  nitrogen  which  he  can  convert  by  some 
chemical  process  into  a  solid  substance  which  in  turn  he  can 
apply  to  the  soil?  After  a  great  many  years  of  experimenta- 
tion, the  last  question  has  been  answered  and  to-day  there 
are  on  the  market  at  least  three  chemical  compounds  con- 
taining nitrogen  secured  directly  from  the  atmosphere. 

Calcium  cyanamide  is  one  of  the  compounds  referred 
to.  It  is  prepared  by  passing  nitrogen  through  closed  re- 
torts containing  powdered  calcium  carbide,  heated  to  a 
temperature  of  1,100^C.  Calcium  cyanamide  and  free 
carbon  are  formed,  the  latter  giving  the  product  its  char- 
acteristic black  color.  It  is  necessary  for  the  success  of  the 
process  that  the  nitrogen  be  free  from  oxygen  before  it  is 
passed  over  the  carbide.  What  chemical  reaction  would 
result  if  the  oxygen  were  not  removed?  How  may  nitro- 
gen be  separated  from  the  oxygen  of  the  air? 

Commercial  calcium  cyanamide  is  a  heavy  black  powder 
with  a  somewhat  disagreeable  odor.  It  is  now  manufactured  in 
America  and  can  be  obtained  in  large  quantities.  The  name 
lime-nitrogen  is  commonly  applied  to  this  substance.  It  con- 
tains 15  to  23%  nitrogen,  40  to  42%  calcium,  17  to  18%  carbon. 

Under  favorable  conditions  the  nitrogen  of  the  cyan- 


218  CHEMISTRY  OF  THE  FARM  AND  HOME 

amide  is  converted  into  ammonia  which  can  be  utihzed  by 
crops.  Under  mifavorable  conditions,  however,  two  other 
substances,  acetylene  and  dicyanamide,  may  be  formed, 
both  of  which  are  toxic  to  plants.  Where  does  the  acety- 
lene come  from?  By  incorporating  the  calcium  cyanamide 
into  the  soil  eight  to  fourteen  days  before  the  seed  is  planted, 
the  possibility  of  this  poisonous  action  may  be  overcome. 
The  value  of  lime-nitrogen  seems  to  be  greatest  upon  heavy 
soils,  but  upon  sandy  soils  it  ranks  very  low. 

Calcium  Nitrate.  This  substance  is  made  from  atmos- 
spheric  nitrogen  in  the  following  manner.  Air  is  passed 
over  electric  arcs  of  a  very  high  power  and  temperature. 
The  nitric  oxide  thus  formed  is  passed  through  milk  of  lime, 
giving  calcium  nitrate.  The  expense  of  the  operation  is. 
governed  almost  entirely  by  the  cost  of  electricity. 

Calcium  nitrate  has  a  yellowish  white  color,  is  easily  soluble 
in  water,  and  deliquesces,  absorbs  moisture,  very  rapidly  from 
the  air.  Are  there  any  objections  to  such  a  property  in  a  ferti- 
lizer? The  difficulties  involved  in  this  deUquescence  are  over- 
come in  two  ways,  first  by  adding  an  excess  of  lime,  second  by 
grinding  the  material  and  parking  in  air-tight  casks.  The 
first  product,  called  basic  calcium  nitrate,  contains  8.9%  nitro- 
gen, while  the  second  product  has  from  11  to  13%  nitrogen. 

Comparing  the  common  property  of  the  nitrates  of 
sodium  and  calcium  of  easily  absorbing  moisture,  what 
predictions  would  you  make  concerning  their  availability  to 
plants  and  their  lack  of  absorption  by  soils? 

Calcium  nitrate  may  be  spread  upon  the  surface  of  the 
ground  as  it  exerts  no  poisonous  action  and  does  not  tend  to 
form  a  crust  as  does  sodium  nitrate. 

Both  calcium  nitrate  and  calcium  cyanamide  are  being 
produced  at  less  cost  per  pound  than  sodium  nitrate  laid 
down  in  the  neighborhood  of  the  factories  in  Europe.  It 
seems,  though,  that  with  improved  processess  the  cost  of 
nitrogen  in  artificial  products  will  be  greatly  reduced. 


FERTILIZERS  219 

Fertilizers  Containing  Organic  Nitrogen.  A  number  of 
commercial  products  of  plant  and  animal  origin  are  valuable 
for  the  nitrogen  they  contain  and  are  used  sometimes  as 
feeding  stuffs  and  sometimes  as  fertilizers.  The  by-pro- 
ducts of  slaughter  houses  are  examples  of  such  materials. 
They  are  dried  blood,  dried  meat,  tankage,  hoof  meal  and 
a  few  other  inferior  products.  Of  these  substances,  dried 
blood  is  the  most  readily  decomposed.  What  effect  would 
that  have  upon  its  availability?  It  produces  results  far 
more  quickly  than  any  other  form  of  organic  nitrogen. 
Moreover,  as  an  animal  product,  it  contains  from  0.9  to  1.8% 
of  phosphorus.  Dried  meat  is  not  decomposed  as  readily, 
but  is  in  fact  utilized  generally  as  feed  for  hogs  or  poultry. 
The  resulting  manure  contains  most  of  the  nitrogen  of  the 
original  meat  so  that  two  purposes  are  served  in  this  way. 

Tankage  is  a  general  mixture  of  refuse  material  from 
slaughter  houses.  It  has  usually  been  steam  cooked  in  order 
to  separate  the  fat  and  gelatine  and  render  the  residue  more 
easily  fermentable  in  the  soil.  It  is  variable  in  its  composi- 
tion, since  it  includes  the  otherwise  unusable  parts  of  the 
carcass,  as  bone,  tendons,  flesh,  hair,  etc.  Concentrated 
tankage  is  obtained  by  evaporating  the  fluids  from  the 
animal  matter  and  is  the  richest  in  nitrogen,  as  well  as  more 
uniform  in  character  than  the  other  forms  of  tankage. 
Because  of  the  fineness  of  division  and  the  physical  charac- 
ter of  the  concentrated  tankage,  it  undergoes  decomposi- 
tion more  readily  than  common  tankage  and  allows  its  nitro- 
gen to  be  more  easily  utilized.  Such  material  contains  from 
10%  to  12%  nitrogen,  but  very  little  phosphorus.  The  in- 
ferior grades  of  tankage  contain  from  4%  to  9%  nitrogen 
and  from  1%  to  5%  phosphorus.  Tankage  varies  so  much 
that  it  is  always  sold  on  the  basis  of  its  composition. 

Hoof  meal  contains  a  large  amount  of  nitrogen,  but  the 
meal  decomposes  very  slowly.  Leather  meal  and  wool  and 
hair  waste  are  so  difficultly  decomposed  that  they  may 


220  CHEMISTRY  OF  THE  FARM  AND  HOME 

retain  their  original  structure  for  years  after  being  placed 
in  the  soil.  All  materials  of  such  character  may,  however, 
be  rendered  more  available  by  treatment  with  sulphuric 
acid.  Would  it  be  of  any  advantage  to  the  farmer  to  know 
whether  the  nitrogen  of  fertilizers  came  from  high  or  low 
grade  materials? 

Dried  blood  contains  from  6%  to  13%  of  nitrogen, 
dried  meat  and  hoof  meal  12%  to  13%,  and  tankage  between 
4%  and  12%,  depending  upon  its  condition  and  grade. 

Ground  fish,  fish  meal,  and  fish  tankage  are  excellent 
forms  of  organic  nitrogen.  They  are  by-products  of  the 
fish  canning  and  packing  industry  and  of  oil  works,  such  as 
the  menhaden  industry.  These  fish  materials  have  a  lower 
per  cent  of  nitrogen  than  blood  or  meat  (8%),  but  it  is 
readily  available,  since  fish  readily  decomposes  in  the  soil. 

Certain  vegetable  products  as  cotton  seed  meal,  linseed 
meal  and  castor  pomace  are  used  as  fertilizers,  though 
they  are  more  often  directly  used  as  feeding  stuffs.  Their 
fertility  constituents  are  then  available  in  the  manure. 
Cottonseed  meal  contains  6%  to  7%  nitrogen,  linseed  meal 
53^%,  and  castor  pomace  6%.  These  meals  decompose 
rather  slowly  in  the  soil  on  account  of  their  oil  content. 
They  contain  some  phosphorus  as  well  as  nitrogen. 

Fertilizers  Used  for  Their  Phosphorus.  There  are  two 
main  classes  of  phosphorus  fertilizers:  the  mineral  phosphates, 
and  those  associated  with  organic  matter.  The  latter  de- 
compose more  quickly  in  the  soil  than  untreated  mineral 
phosphates  on  account  of  bacterial  action  upon  them.  Some 
animal  and  vegetable  products  used  for  nitrogen  also  contain 
phosphorus.     Name  some  that  have  been  mentioned. 

Bone  phosphate  is  used  in  several  forms.  Raw  and 
steamed  bone,  either  ground  or  unground,  and  bone  tank- 
age are  the  more  common  forms;  bone  black  and  bone  ash 
are  also  used  after  having  served  other  purposes  first.  The 
more  finely  ground  the  bones,  the  more  quickly  they  are 


FERTILIZERS  221 

available.  Why?  The  steaming  process  also  facilitates  the 
availability  of  bones,  inasmuch  as  it  frees  them  from  fat 
and  nitrogenous  matter  and  produces  a  better  mechanical 
condition.  The  form  of  phosphorus  in  all  these  materials 
is  the  same,  namely  tricalcium  phosphate  Cas  (PO4)  2  •  AH 
these  carriers  of  phosphorus  are  slow  acting  and  should  be 
used  for  the  permanent  upbuilding  of  the  soil  fertility  rather 
than  as  an  immediate  source  of  phosphorus. 

Raw  bones  contain  9.5%  phosphorus  and  4%  nitrogen; 
steamed  bones  contain  12%  to  15%  phosphorus  and  13^% 
nitrogen;  and  bone  tankage  contains  3%  to  4%  phosphorus. 

Mineral  Phosphates.  There  are  a  number  of  natural 
deposits  of  mineral  phosphates  in  different  portions  of  the 
world,  some  of  the  most  important  of  which  are  in  North 
America.  The  form  in  which  the  phosphorus  exists  in  these 
deposits  is  tricalcium  phosphate,  but  a  variety  of  substances 
is  associated  with  it.  South  Carolina  phosphate  contains 
11  to  12%  phosphorus  with  but  a  very  small  amount  of  iron 
and  alumina.  Florida  phosphates  occur  in  the  forms  of  soft 
phosphate,  pebble  phosphate  and  boulder  phosphate.  Soft 
phosphate  contains  8  to  13%  phosphorus.  It  is  more  easily 
ground  than  most  of  these  rocks  and  is  often  applied  to  the 
land  without  being  converted  into  a  superphosphate.  Ten- 
nessee phosphate  contains  from  13  to  15%  phosphorus. 

Basic  slag,  phosphate  slag  or  Thomas  phosphate  is  a 
by-product  in  the  manufacture  of  steel  from  pig  iron  rich 
in  phosphorus.  The  phosphorus  is  present  in  the  form  of 
tetracalcium  phosphate,  (CaO)4P205.  It  also  contains 
calcium,  magnesium,  aluminium,  manganese,  silicon,  and 
sulphur.  Basic  slag,  when  ground,  may  be  applied  directly 
to  the  soil,  because  its  phosphorus  is  more  readily  soluble 
than  the  tricalcium   phosphate. 

Superphosphate  Fertilizers.  These  are  prepared  by 
treating  bone  and  mineral  phosphates  with  sulphuric  acid, 
the  object  being  to  render  the  phosphorus  of  such  materials 


222  CHEMISTRY  OF  THE  FARM  AND  HOME 

more  readily  available  to  plants.  Part  of  the  calcium  is 
replaced  by  hydrogen  and  monocalcium  phosphate  is  formed. 
Calcium  sulphate  is  another  product  along  with  a  small 
amount  of  dicalcium  phosphate.  Some  sulphuric  acid  is 
also  consumed  in  this  treatment  by  the  impurities  present 
in  the  phosphate  rock.  Calcium  and  magnesium  carbonates, 
iron  and  aluminium  phosphates,  calcium  chloride  and  cal- 
cium fluoride  are  the  principal  impurities.  They  use  up 
more  or  less  of  the  acid,  depending  upon  their  quantity, 
and  give  sulphates  of  calcium,  magnesium,  iron  and  alumi- 
nium. Would  you  regard  the  presence  of  such  impurities 
of  any  importance  in  the  manufacturing  process?     Why? 

Monocalcium  phosphate,  acid  phosphate  or  super- 
phosphate, CaH4(P04)2  has  the  same  value  in  both  bone 
and  rock  material.  But  the  tricalcium  phosphate  of  bones 
is  more  valuable  than  that  of  rock  phosphate.  Bone  super- 
phosphate contains  about  5%  available  phosphorus.  Rock 
superphosphate  varies  from  5%  to  8%  available  phosphorus, 
depending  upon  the  source  of  the  mineral. 

Double  superphosphates  contain  twice  as  much  avail- 
able phosphorus  as  those  made  in  the  ordinary  way.  Poorer 
grades  of  phosphate  rock  are  treated  with  sulphuric  acid 
and  the  soluble  phosphoric  acid  and  excess  of  sulphuric 
acid  are  separated  by  filtering  from  the  mass.  This  solution 
is  then  used  to  treat  phosphate  rock  rich  in  tricalcium 
phosphate.  Double  superphosphate  is  the  most  concen- 
trated material  containing  available  phosphorus. 

Reverted  Phosphoric  Acid.  When  part  of  the  phos- 
phoric acid  of  superphosphates  becomes  less  easily  soluble, 
the  value  of  the  fertilizer  is  decreased.  This  change  is  called 
reversion.  It  is  much  more  likely  to  occur  in  superphosphate 
made  from  rock  phosphate  than  in  that  made  from  bone 
phosphate.  It  is  due  to  reaction  of  an  excess  of  tricalcium 
phosphate  or  of  calcium  from  impurities  with  monocalcium 
phosphate  to  form  the  less  soluble  dicalcium  phosphate. 


FERTILIZERS 


223 


Relative  Availability  of  Phosphate  Fertilizers.       Both 

the  superphosphates  and  double  superphosphates  con- 
tain their  phosphorus  in  a  form  in  which  it  can  be  taken 
up  by  the  plant  at  once.  They  can  be  applied,  therefore, 
either  before  planting  or  along  with  planting  or  when  the 
crop  is  growing.  Crude  phosphates  need  to  be  applied 
sometime  before  the  phosphorus  is  needed  by  crops.  The 
phosphorus  of  rock  materials  becomes  available  only  through 
the  natural  dissolving  processes  of  the  soil.  The  presence 
of  decomposing  organic  matter  is  a  great  aid  to  this  process. 
Reverted  phosphates  are  believed  to  be  quite  available 
to  plants,  but  not  as  readily  so  as  the  superphosphates. 
The  degree  of  fineness  to  which  the  material  is  ground 
makes  a  great  difference  in  the  availability  of  the  less  soluble 
phosphate  fertilizers,  especially  in  the  ground  rock  and  bone 
phosphates.  These  materials  should  be  ground  fine  enough 
to  pass  through  a  sieve  having  meshes  1-50  of  an  inch  in 
diameter.  In  this  condition  a  large  surface  of  the  fertilizer 
is  subject  to  attack  by  the  soil  solvents. 


Figure  64.     Mining  kainite. 


224  CHEMISTRY  OF  THE  FARM  AND  HOME  . 

Fertilizers  Used  for  Their  Potassium.  Potassium  ferti- 
lizers are  largely  produced  in  Germany  from  natural  sources, 
known  as  the  Stassfurt  salt  deposits.  Other  deposits  have 
been  found  lately  in  Germany  and  efforts  are  being  made 
in  the  United  States  to  locate  salt  deposits  which  contain 
potassium.  Wood  ashes  were  formerly  used  as  a  carrier 
of  potassium. 

Stassfurt  Salts.  The  potash  deposits  at  Stassfurt  con- 
sist of  a  number  of  minerals.  Kainite  is  mined  in  the 
largest  quantity.  Sylvinite,  carnallite  and  kieserite  are  other 
examples  of  these  minerals.  They  are  usually  mixtures 
of  a  number  of  salts  as  sulphates  and  chlorides  of  magnesium, 
potassium  and  sodium.  The  minerals  may  be  merely 
crushed  and  powdered,  in  which  case  the  fertilizer  is  a  mix- 
ture of  the  chemicals  named  above,  or  the  potassium 
salts  may  be  separated  from  the  other  substances  by  solu- 
tion and  crystallization.  The  mixture  of  crushed  minerals 
is  a  low  grade  potassium  fertilizer,  containing  from  10% 
to  16%  potassium  in  kainite.  The  purified  chloride  and 
sulphate  contain  respectively  41%  and  42%  potassium. 

Potassium  chloride,  muriate  of  potash,  KCl,  has  the 
advantage  of  being  more  diffusible  in  the  soil  and  less  ex- 
pensive than  the  sulphate.  But  the  chloride  has  an 
injurious  action  on  certain  crops,  such  as  tobacco,  sugar 
beets  and  potatoes.  The  sulphate  is  not  injurious  to  crops. 
Kainite  should  be  applied  to  the  soil  a  considerable  time 
before  the  crop  is  planted,  as  the  chlorides  present  in  the 
material  may  injure  the  vitality  of  the  seed. 

Wood  Ashes.  Wood  ashes  formerly  constituted  a 
large  portion  of  the  supply  of  potassium  fertilizers.  The 
potassium  is  present  in  the  form  of  carbonate  which  is 
alkaline  in  its  reaction  and  may  be  injurious  to  seeds.  Un- 
leached  wood  ashes  contain  about  4.5%  potassium,  0.9% 
phosphorus  and  21.5%  calcium.  Leached  wood  ashes 
contain  0.8%  potassium,  0.7%  phosphorus  and  20.0%  to 


FERTILIZERS  225 

20.7%  calcium.  The  presence  of  these  other  constituents 
adds   to   the   value   of   the   ashes. 

Complete  Fertilizers.  There  are  a  number  of  materials, 
as  already  indicated,  carrying  nitrogen,  phosphorus  and 
potassium,  which  are  used  as  fertilizers.  If  a  soil  is  known 
to  be  lacking  in  available  nitrogen,  a  material  which  con- 
tains nitrogen  may  be  used  to  supply  the  deficiency,  sim- 
ilarly, in  the  case  of  phosphorus  and  potassium.  If,  on 
the  other  hand,  a  soil  is  deficient  in  any  two  or  three  avail- 
able fertilizing  constituents,  then  a  complete  fertilizer  may 
be  used.  When  it  is  considered  that  there  is  a  number 
of  materials  containing  nitrogen,  or  phosphorus,  or  potas- 
sium, and  that  the  properties  of  these  substances  differ 
considerably;  also  that  there  are  many  different  types  of 
soils  and  crops  for  which  the  fertilizers  may  be  used,  the 
complexity  of  fertilizer  practice  may  partly  be  realized. 
Each  manufacturer  of  commercial  fertilizers  places  on  the 
market  a  number  of  brands  that  have  some  trade  name. 
This  frequently  implies  the  usefulness  of  the  fertilizer 
for  some  particular  crop,  but  may  not  take  into  considera- 
tion the  character  of  the  soil  upon  which  it  may  be  applied. 
If  the  substances  used  in  the  fertilizer  are  difficultly  solu- 
ble, the  fertilizer  is  not  so  valuable  as  if  composed  of  easily 
soluble  substances.  It  is  important  that  the  purchaser 
should  know  the  solubility  and  the  percentage  of  each  in- 
gredient in  the  fertilizer. 

Fertilizer  Inspection.  In  order  to  protect  the  consumer 
state  laws  regulating  the  sale  of  fertilizers  have  been  estab- 
lished. State  laboratories  collect  and  analyze  samples  of  all 
fertilizers  sold  and  make  certain  that  the  guarantee  of  the 
manufacturer  is  correct.  Reports  of  such  inspection  are  issued 
regularly  as  bulletins  from  the  experiment  stations  and  aid 
the  consumer  in  his  purchase  of  reliable  brands  of  fertilizers. 

Fertilizer  Terms.  To  add  to  the  general  complexity 
of  fertilizer  practice,   there  is  an   unfortunate  system  of 

15— 


226  CHEMISTRY  OF  THE  FARM  AND  HOME 

nomenclature  which  increases  the  difficulty  of  the  farmer's 
understanding  the  labels  on  a  fertihzer  sack.  Instead  of 
the  names  of  the  elements,  ammonia  (NH3)  replaces  nitro- 
gen (N);  phosphoric  acid  (P2O5)  and  bone  phosphate  of 
lime  (Ca3(P04)2)  replace  phosphorus  (P);  and  potash 
(K2O)  and  sulphate  of  potash  (K2SO4)  replace  potassium 
(K).  The  student  will  readily  appreciate  the  fact  that  the 
quantity  of  these  compounds  is  greater  than  the  quantity 
of  the  elements  alone.  Therefore  the  amount  or  percentage 
of  such  constituents  appearing  on  a  fertilizer  sack  is  greater 
than  if  only  the  element  were  indicated.  What  false  im- 
pression would  this   cause? 

By  considering  the  atomic  and  molecular  weights  of 
these  substances  it  is  possible,  however,  to  compute  their 
quantitative  relation.  For  example,  the  atomic  weight  of 
nitrogen  is  14  and  of  hydrogen  is  1.  Therefore  in  the  form- 
ula of  ammonia  (NH3)  the  molecular  weight  is  17.  The 
relation  of  nitrogen  to  ammonia  is  then  14  to  17,  or  as  0.8235 
to  1.0.  If  the  percentage  of  ammonia  is  given  as  10.0,  the 
percentage  of  nitrogen  is  0.8235  times  that,  or  8.235.  The 
figure  0.8235  is  called  a  factor.  Similarly,  the  factors  of 
the  other  ratios  may  be  shown  to  be  (1)  phosphorus  is  to 
phosphoric  acid  as  0.436  is  to  1.0  and  (2)  potassium  is  to 
potash  as  0.83   is  to   1.0. 

Values  of  Fertilizers.  In  addition  to  the  inspection 
and  analysis  of  fertilizers,  several  states  make  an  estimate 
of  their  financial  value.  They  adopt  a  schedule  of  trade 
values  for  the  different  forms  of  nitrogen,  phosphorus  and 
potassium.  These  values  are  based  on  the  cost  of  the  un- 
mixed constituents  and  are  secured  by  averaging  the  whole- 
sale prices  per  ton  of  all  the  various  fertilizer  supplies  for 
the  six  months  preceding  March  1,  to  which  is  added  about 
20%  to  cover  manufacturers'  cost,  etc.  The  trade  values 
for  a  few  of  the  forms  of  plant  food  for  the  year  1914  are 
as  follows: 


FERTILIZERS  .         227 

Value  in  cents 
per  pound 

Nitrogen  as  nitrates 14.0 

Nitrogen  in  ammonium  salts 13.0 

Nitrogen  in  high  grade  organic  material 16.5 

Phosphoric  acid,  soluble  in  water 5.0 

Phosphoric  acid,  insoluble,  in  fine  bone 3.0 

Potash,  as  sulphates 5.0 

The  commercial  value  of  a  fertilizer  may  be  found  if 
the  percentage  of  each  constituent,  its  form  and  availability, 
and  the  trade  value  of  such  forms  are  known.  For  example, 
here  is  a  fertilizer  which  cost  $42.00  a  ton  and  had  the  fol- 
lowing composition: 

Nitrogen  in  sodium  nitrate 4% 

Phosphoric  acid,  soluble  in  water 6% 

Phosphoric  acid,  insoluble^  in  fine  bone 22% 

Potash,  as  sulphate 8% 

The  number  of  pounds  of  each  constituent  per  ton  of  ferti- 
lizer is  then  found  to  be 

Nitrogen  in  sodium  nitrate 4%  of  2,000=   80 

Phosphoric  acid,  soluble 6%  of  2,000  =  120 

Phosphoric  acid,  insoluble 22%  of  2,000  =  440 

Potash,  as  sulphate 8%  of  2,000  =  160 

Applying  the  trade  values  to  these  several  constituents, 

Nitrogen  as  nitrates 80X0.14  =$11.20 

Phosphoric  acid,  soluble 120  X 0.05  =     6.00 

Phosphoric  acid,  insoluble 440X0.03  =    13.20 

Potash,  as  sulphate 160X0.05  =     8.00 

Total $38.40 

The  computed  value  can  then  be  compared  with  the  com- 
mercial value.  As  a  rule  the  commercial  value  and  the  trade 
value  of  high  grade  fertilizers  more  nearly  coincide  than 
those  of  low  grade  mixtures.  In  other  words,  it  is  a  good 
business  policy  to  buy  high  grade  materials  of  high  cost 
than  low  grade  and  cheap  fertilizers. 

Home  Mixing.  Several  experiment  stations  have  shown 
that  it  is  possible  to  buy  and  mix  fertilizers  on  the  farm  with 
as  good  results  as  can  be  obtained  with  mixtures  that  are 
bought.     This  procedure  has  several  advantages,  namely, 


228  CHEMISTRY  OF  THE  FARM  AND  HOME 

it  is  claimed  to  be  cheaper  than  the  purchase  of  ready 
mixed  fertihzers,  the  farmer  can  ascertain  by  field  tests 
the  best  proportions  of  the  various  fertilizer  constituents 
to  use  on  his  land,  and  he  can  know  the  character  of  the 
material  he  is  using.  There  are  the  disadvantages,  however, 
that  it  is  not  always  possible  to  obtain  the  simple  constit- 
uents and  that  it  is  relatively  more  difficult  to  properly 
blend  the  materials  of  the  mixture  on  the  farm  than  by  the 
use    of   fertilizer   machinery. 

Soil  Amendments.  Those  substances  which  are  added 
to  soils  to  increase  their  productive  capacity  by  affecting 
the  physical  structure  of  the  soil  as  well  as  its  chemical 
and  bacteriological  properties  are  called  soil  amendments. 
The  principal  chemical  substances  used  for  this  purpose 
are  calcium  salts,  especially  calcium  carbonate  and  calcium 
sulphate.  The  former  is  of  the  greatest  importance  in  con- 
nection with  soil  fertility.  It  not  only  serves  to  cause  the 
granulation  and  flocculation  of  clay  soils,  but  also  to  bind 
the  particles  of  a  sandy  soil  together.  Limestone  also  neu- 
tralizes the  acidity  of  the  soil  and  thereby  improves  the  con- 
ditions for  soil  bacteria.  Again  lime  seems  to  have  the 
effect  of  liberating  plant  food  constituents  which  are  not 
in  a  readily  available  form,  such  as  phosphorus  and  potas- 
sium. Gypsum,  calcium  sulphate,  was  thought  to  have  this 
same  effect  of  hberating  plant  food,  especially  potassium. 
It  is  also  used  to  neutralize  black  alkali,  but  has  no  effect 
upon  soil  acidity.  Gypsum  seems  to  have  some  influence 
upon  the  physical  properties  of  the  soil,  but  not  as  marked 
as  limestone.  The  reaction  upon  sodium  carbonate,  or 
black  alkaU,  is  interesting  in  that  it  is  the  same  as  is 
used  in  the  softening  of  water  by  the  addition  of  wash- 
ing soda. 

CaS04  +  NagCOs  -^  CaCOs  +  Na2S04 
Sodium  sulphate,  or  white  alkaU,  is  not  as  toxic  to  plants 
as  the  black  alkali. 


FERTILIZERS  229 

Methods  of  Application.  In  order  to  secure  the  maxi- 
mum efficiency  of  a  fertilizer,  it  is  necessary  to  apply  it  to 
the  soil  in  such  a  manner  that  the  plant  food  constituents 
are  most  thoroughly  and  uniformly  distributed  throughout 
the  feeding  range  of  the  crop  roots.  For  this  purpose  spec- 
ial machinery  is  available  to  distribute  the  fertilizer  either 
in  rows,  beside  the  rows,  or  broadcast  uniformly  over  the 
enfcire  surface.  Many  drills  and  planters  are  provided 
with  special  attachments  for  fertilizer  application,  but  an 
ordinary  grain  drill  may  serve  fairly  well  for  broadcasting 
the  material.  The  rate  of  application  varies  from  200  to 
600  pounds  per  acre,  the  average  being  about  400  pounds. 

Choice  of  Fertilizers  for  Specific  Soil  Types.  The 
character  of  the  soil,  in  certain  cases,  often  indicates  what 
plant  food  may  be  lacking.  Clay  soils  are  usually  well 
supplied  with  potassium,  but  are  likely  to  be  deficient  in 
phosphorus.  Sandy  soils  not  only  often  lack  potassium  but 
phosphorus  as  well.  The  same  lack  is  true  of  many  gravelly 
soils.  Peaty  soils  are  generally  rich  in  nitrogen,  but  are 
deficient  in  potassium  and  phosphorus.  The  nitrogen 
compounds,  however,  are  not  quickly  available.  In  the 
numerous  mixed  types  of  soils,  and  most  soils  are  of  this 
character,  these  general  statements  do  not  apply. 

Choice  of  Fertilizers  for  Specific  Crops.  Among  the 
differences  in  the  individual  characteristics  of  crops  the 
feeding  power  of  the  crop  affects  the  choice  of  the  fertilizer. 
Agricultural  plants  may  be  conveniently  divided  into  sev- 
eral different  classes,  the  members  of  which,  while  differing 
in  many  ways,  have  in  common  certain  resemblances  that 
are  of  importance  in  this  connection. 

(1)  Cereal  crops  are  comparatively  shallow  rooted  and 
occupy  the  upper  layer  of  soil  extensively  before  the  end  of 
the  season.  Consequently  fertilizers  for  such  crops  are 
most  effectively  applied  in  the  upper  layer  of  soil,  especially 
if  they  are  very  soluble.     Barley,   oats,   rye    and  wheat 


230  CHEMISTRY  OF  THE  FARM  AND  HOME 

need  a  large  proportion  of  their  nitrogen  in  the  early  part 
of  the  growing  season.  Nitrate  nitrogen  is  usually  found 
most  beneficial,  because  there  is  a  lack  of  this  constituent 
until  after  the  soil  becomes  warm.  Corn,  on  the  other  hand, 
which  makes  its  best  growth  after  the  other  cereals  have 
matured,  can  utilize  organic  forms  of  nitrogen.  The  nitri- 
fication of  such  materials  is  most  active  by  the  time  the  corn 
crop  makes  its  greatest  demands.  All  cereals  are  generally 
benefited  by  the  application  of  acid  phosphate.  Barley, 
especially,  needs  such  a  fertilizer,  owing  to  its  compara- 
tively shallow  root  system. 

(2)  Leguminous  crops  are  vigorous  feeders  and  are  aided 
greatly  by  their  long  roots  which  go  deep  down  into  the  soil. 
In  spite  of  their  ability  to  derive  nitrogen  from  the  air, 
their  chief  characteristic  property,  small  applications  of 
available  nitrogen  are  beneficial  upon  poor  soils,  particularly 
in  the  case  of  alfalfa.  Calcium,  potassium  and  phosphorus 
are  very  effective  with  legumes  upon  most  soils. 

(3)  Grass  crops  are  generally  shallow  rooted  and  con- 
sequently have  a  narrow  feeding  range.  Permanent  mead- 
ows and  pastures  are  greatly  benefitted  by  fertilizers, 
nitrogen  in  soluble  forms  being  especially  useful,  because  the 
growth  of  the  stems  and  leaves  is  largely  dependent  upon 
this  element;  but  nitrification  is  very  slow  in  soil  that  has 
been  occupied  by  a  crop  longer  than  one  year. 

(4)  Orchard  crops  collect  their  food  both  from  a  consid- 
erable area  and  depth  of  soil.  They  need  a  continuous 
supply  of  plant  food  in  moderate  amounts  and  in  fairly 
soluble  form.  Care  should  be  used,  however,  not  to  ferti- 
lize in  such  a  manner  as  to  make  rapid  growth  of  new  wood 
or  to  prolong  the  growth  till  too  late  in  the  fall. 

(5)  Root  crops  obtain  their  food  from  a  comparatively 
limited  area.  Fertilizers  must  be  supplied  them  in  fairly 
soluble  forms.  Turnips  respond  to  phosphorus  and  carrots 
and  beets  to  nitrogen  compounds. 


FERTILIZERS  231 

(6)  The  chief  purpose  in  growing  garden  crops,  in  most 
cases,  is  the  production  of  leaves  and  stalks  of  a  tender  suc- 
culent character.  This  quality  depends  upon  rapidity  of 
growth  and,  therefore,  an  abundance  of  soluble  nitrogen 
is  essential.  Enough  available  phosphorus  and  potassium 
must  be  furnished  to  allow  the  nitrogen  to  accomplish  its 
maximum  work.  Farm  manure  is  used  for  such  crops  and 
often  in  large  quantity. 

In  general  it  may  be  said  that  for  crops  whose  root  sys- 
tems extend  sideways  in  every  direction  it  is  preferable  to 
broadcast  the  fertilizer  and  harrow  it  into  the  ground  before 
planting.  In  the  case  of  crops  whose  root  systems  extend 
downward  it  is  advisable  to  distribute  the  added  plant 
food  in  or  near  the  rows  or  hills.  Concentrated  fertilizers, 
however,  may  injure  seeds  and  young  plants;  hence  such 
substances  must  be  kept  from  coming  into  direct  contact 
with  the  seedling. 

Those  plant  food  materials  which  are  easily  soluble, 
diffuse  through  the  soil  readily,  and  are  not  well  retained 
by  the  soil  should  be  applied  only  when  the  crop  is  ready  to 
use  them.  Nitrogen  in  the  form  of  nitrates  is  especially 
liable  to  loss.  Fertilizers  which  do  not  dissolve  readily 
should  be  applied  early  in  the  season  and  worked  into  the 
soil  in  order  to  be  decomposed  and  made  available  for 
the  crop. 

Systems  of  Fertilization.  There  are  many  factors  which 
modify  the  effect  of  fertilizers,  such  as  the  soil,  the  crop 
and  climatic  conditions.  It  is  difficult,  therefore,  to  pre- 
scribe general  rules  for  applying  these  plant  food  constit- 
uents. Farmers  should  study  their  own  conditions,  try 
various  combinations,  and  use  the  materials  that  give  the 
most  profitable  results  under  their  conditions.  After  ascer- 
taining this  necessary  information  they  should  then  adopt 
a  systematic  method  of  fertilization.  It  must  be  remem- 
bered, moreover,  that  this  system  should  include  a  rotation 


232  CHEMISTRY  OF  THE  FARM  AND  HOME 

of  crops,  the  liberal  use  of  farm  or  green  manure  and  all 
other  aids  to  better  farming.  Some  of  the  more  common 
systems  of  fertilization  are  given  below. 

(1)  The  system  based  on  the  influence  of  a  single  element. 
It  is  assumed  that  plants  can  be  divided  into  three  groups, 
one  group  being  most  benefited  by  nitrogen,  another  by  phos- 
phorus, and  another  by  potassium.  Nitrogen  is  said  to  be 
the  ruling  element  for  small  grains,  meadow  grass  and  beet 
crops.  Phosphorus  is  the  important  element  for  corn, 
sorghums  and  turnip  crops.  Potassium  is  dominant  for  the 
legumes,  flax  and  potatoes.  If  the  soil  is  fertile,  the  domi- 
nant element  is  supplied  to  force  a  maximum  growth  of  the 
crop.  If  the  soil  is  not  fertile,  liberal  portions  of  the  domi- 
nant element  are  supplemented  by  moderate  additions  of 
the   other   plant   foods. 

(2)  The  system  based  on  the  necessity  of  an  abundant 
supply  of  the  fertilitizer  elements.  This  method  is  useful 
in  building  up  a  very  poor  soil  when  accompanied  by  a  rota- 
tion and  the  application  of  manure.  Potassium  and  phos- 
phorus are  relatively  cheap  and  easily  retained  by  the  soil, 
but  nitrogen  is  expensive  and  easily  lost.  Hence  a  reason- 
able excess  of  potassium  and  phosphorus  is  applied  to 
more  than  satisfy  the  maximum  needs  of  any  crop  and  then 
the  nitrogen  is  applied  in  an  available  form  and  at  such  times 
as  will  insure  the  minimum  loss  of  the  element  and  the 
maximum  growth  of  the  plant.  The  phosphorus  and  potas- 
sium may  be  supplied  in  their  cheapest  forms. 

(3)  The  system  based  on  the  amount  of  plant  food  taken 
up  by  the  crop.  This  method  requires  that  different  plants 
be  fertilized  in  the  proportion  in  which  chemical  analysis 
shows  the  three  elements,  nitrogen,  phosphorus  and  potas- 
sium, to  exist  in  the  plant.  If  an  abundance  of  plant  food 
is  furnished,  the  system  may  be  profitable;  but  it  is  not 
so  for  ordinary  farm  crops.  It  does  not  consider  the  facts 
that  plants  vary  in  their  power  of  absorbing  different  ele- 


FERTILIZERS  233 

ments  and  that  the  period  of  growth  exercises  some  effect 
upon  the  plant's  abiUty  to  acquire  food. 

(4)  The  system  based  on  the  money  crop  in  a  rotation. 
The  most  profitable  crop  in  the  rotation  is  supplied  with 
an  abundance  of  the  fertilizer  in  order  to  insure  continuous 
feeding  and  maximum  production.  The  remaining  crops 
or  those  immediately  succeeding  in  the  rotation  are  nourished 
by  the  fertilizer  residues,  with  further  small  applications,  if 
necessary.  This  method  has  the  advantage  of  being  the 
most  practical  of  all,  that  is,  the  most  certain  of  giving  pro- 
fitable returns.  The  other  methods  are  as  yet  subject  to 
uncertain  returns,  due  to  the  changing  effects  of  environ- 
ment and  unknown  properties  of  the  different  plants. 


SUMMARY 

Fertilizers  are  used .  for  the  plant  food  constituents,  nitrogen, 
phosphorus  and  potassium,  which  they  contain.  There  are  many 
different  kinds  of  carriers  of  these  substances  and  they  vary  in  solu- 
bility, availabiUty  and  effect  upon  crops  and  soils.  Fertihzers  are 
mined  from  deposits,  they  are  manufactured  from  the  air,  and  they 
are  derived  as  by-products  of  certain  industries  like  those  of  packing 
houses  and  chemical  works.  The  raw  materials  of  fertilizers  may  be 
treated  to  make  them  more  available  to  crops.  Sulphuric  acid  is  espec- 
ially   useful    for    this    purpose. 

The  use  of  fertilizers  is  not  a  simple  matter.  The  character  of 
the  material  itself,  of  the  crop  and  of  the  soil  must  all  be  taken  into 
consideration.  In  order  to  aid  the  consumer  a  rigid  fertilizer  inspection 
is  enforced  by  law  in  the  various  states.  This  ensures  the  consumer's 
securing  goods  up  to  the  guarantee  and  within  a  reasonable  amount 
of  the  actual  commercial  value  of  the  constituents.  It  is  possible  for 
the  farmer  to  study  his  own  soil  needs  and  mix  his  own  fertilizer. 

Other  substances  are  applied  to  soils,  but  not  for  the  purpose  of 
adding  plant  food.  They  act  as  stimulants  or  amendments.  The 
most  notable  example  is  calcium  carbonate  which  improves  the  phys- 
ical tilth  of  soils,  betters  the  bacteriological  conditions  and  helps 
liberate  plant  food. 


234  CHEMISTRY  OF   THE  FARM  AND  HOME 

QUESTIONS 

1.  Name  the  elements  which  are  necessary  for  plant  and  animal 
life. 

2.  What  substances,  that  are  necessary  for  plant  life,  are  liable 
to  be  absent  from  soils  and  how  may  they  be  supplied? 

3.  Name  ten  common  ingredients  of  commercial  fertilizers,  stat- 
ing their  source  and  the  constituent  of  fertilizing  value. 

4.  Which  class  of  fertilizers  do  you  consider  of  the  greatest 
importance  and  why? 

5.  Why  is  it  necessary  to  know  the  analysis  and  guarantee  of 
a  commercial  fertilizer? 

6.  As  a  general  rule  is  it  advisable  to  use  low  grade  fertilizers? 

7.  How  does  the  use  of  calcium  carbonate  differ  from  that  of 
a  nitrogenous  or  phosphatic  fertiUzer? 

8.  What  are  some  of  the  factors  that  affect  the  availability  of 
fertilizers? 

9.  What  are  some  of  the  principal  factors  which  must  be  con- 
sidered in  the  application  of  fertihzers? 

10.  Is  it  necessary  to  use  other  methods  along  with  fertiliza- 
tion in  the  effort  to  upbuild  the  soil  fertility?     State  reasons. 

11.  Would  you  advise  (a)  adding  calcium  sulphate  to  overcome 
the  acidity  of  a  soil;  (b)  adding  a  potassium  fertilizer  to  a  clay  soil; 
(c)  a  phosphorus  fertilizer  to  a  soil  to  be  cropped  to  small  grains? 
State  reasons. 

12.  What  in  your  opinion  is  the  chief  point  to  keep  in  mind 
for  maintaining  the  fertility  of  the  soil  of  your  farm?  Tell  why  you 
think  so  and  the  method  of  meeting  this  problem. 


CHAPTER  IX 
FARM  MANURE 


Fertilizing  Importance  of  Manure.  When  farmers  know 
the  composition  and  properties  of  manure  which  determine 
its  great  value  to  crops,  such  wasteful  methods  of  handling 
it  as  are  shown  in  Figure  65  will  be  replaced  by  efforts  to 

obtain  from  this  mate- 
rial the  greatest  possible 
value.  Our  present  pur- 
pose is  to  learn  the  chem- 
ical principles  by  which 
the  conservation  of  its 
properties  may  be  ac- 
complished. 

As  we  have  previously 
learned  in  our  study  of 
the  plant,  certain  ele- 
ments essential  to  its 
growth  are  obtained  from 
the  soil.  Is  it  not  quite  natural  to  question  whether  the 
soil  can  continue  to  supply  these  elements  and  support  crops 
indefinitely?  It  was  believed  by  some  early  agricultural 
scientists  that  tillage  alone  was  sufficient  to  maintain  the 
crop-producing  power  of  the  soil;  but  we  know  now,  that, 
among  other  things,  the  supply  of  plant  food  must  be  kept 
up.  This  fact  is  the  basis  for  the  use  of  commercial  fer- 
tilizers about  which  we  have  learned  already.  Some  of 
these  fertilizers,  you  will  recall,  act  directly  by  increasing 
the  supply  of  plant  food,  while  others  act  indirectly  in 
various  ways,  such  as  favoring  the  growth  of  helpful  bac- 

235 


Figure  65.  Loss  of  value  in  manure  by 
leaching.  The  water  running  from  this 
large  roof  washes  the  best  of  the  plant  food 
from  the  manure. 


236  CHEMISTRY  OF  THE  FARM  AND  HOME 

teria.  Farm  manure  is  the  most  generally  useful  and  pop- 
ular fertilizer,  because  it  combines  most  of  the  valuable 
properties  of  commercial  fertilizers.  Perhaps  the  reasons 
for  the  superior  value  of  farm  manure  as  a  fertilizer  will 
become  clearer,  if  we  consider  its  source. 

Source  of  Farm  Manure.  The  food  eaten  by  farm 
animals  is  a  mixture  of  plants  and  plant  products.  It  con- 
tains essential  elements  in  the  proportions  in  which  they 
are  taken  from  the  soil  by  plants.  What  is  nature's  method 
for  returning  these  elements  from  the  plant  to  the  soil  on 
wild,  virgin  land?  After  the  action  of  the  digestive  juices 
they  are  present  in  farm  manure  as  products  of  partial 
decay.  In  the  cycle  of  plant  food  from  the  air  and  the  soil 
through  the  plant  and  animal  and  back  to  its  sources  they 
are  at  the  early  stages  of  the  return.  Processes  of  fermen- 
tation and  decay  tend  to  return  them  rapidly  from  the 
manure  to  their  original  sources  in  the  air  and  soil.  They 
are,  one  may  say,  in  a  very  active  and  useful  state  which 
they  have  reached  only  by  complex  and  gradual  chemical 
changes.  To  permit  them  by  carelessness  to  become  free 
again  would  be  a  serious  waste  of  chemical  energy.  To 
allow  their  valuable  compounds  in  the  manure  to  be  lost 
would  be  an  extravagant  waste  of  plant  food. 

In  our  study  of  fertilizers  we  have  learned  that  the 
essential  elements  of  greatest  practical  importance  in  plant 
growth  are  nitrogen,  phosphorus,  and  potassium.  As  de- 
scribed in  the  chapter  on  the  plant,  they  are  present  in  both 
organic  and  inorganic  compounds.  By  the  processes  of 
digestion,  which  will  be  described  in  the  next  chapter,  these 
compounds  are  partly  changed  to  soluble  products.  The 
undigested  portion  of  the  food  is  excreted  as  soUd  matter, 
or  dung.  Most  of  the  phosphorus,  which  becomes  waste 
material  after  use,  is  also  excreted  in  the  compounds  of  the 
dung.  On  the  other  hand,  the  waste  potassium  and  nitro- 
gen are  excreted  by  way  of  the  kidneys  and  bladder  in  the 


FARM  MANURE  237 

urine.  The  potassium  is  excreted  as  the  base  of  various 
inorganic  salts,  while  the  nitrogen  is  contained  in  organic 
compounds  derived  from  the  protein  and  closely  related  to 
ammonia.  You  will  see,  then,  that  the  manure  consists  of 
two  distinct  parts:  (1)  The  liquid  portion,  which  con- 
tains plant  food  readily  available  for  crops;  and  (2)  the  solid 
portion,  which  contains  compounds  from  which  plant  food 
is  liberated  only  by  chemical  changes  of  decay. 

Farm  manure  bears  to  farming  the  relation  which  by- 
products bear  to  many  commercial  industries.  A  by-pro- 
duct is  a  substance  obtained  as  a  side  issue  from  the  main 
products,  such  as  cottonseed  oil  from  the  cotton  industry. 
The  profits  and  success  of  many  manufacturing  operations 
depend  upon  the  marketing  of  their  by-products.  For  this 
reason,  neglect  of  farm  manure  may  cause  failure,  where 
prudent  use  of  it  would  insure  successful  farming. 

Amount  of  Manure  Product.  If  we  note  the  amount  of 
total  excrement  produced  by  a  single  animal,  we  shall  find 
it  small  for  some  animals.  A  hen,  for  example,  produces 
only  about  two  tenths  of  a  pound  per  day,  and  a  sheep  five 
pounds.  The  cow,  however,  produces  the  considerable 
amount  of  about  seventy  pounds.  When  we  take  into 
account  the  accumulation  of  the  manure  from  day  to  day, 
the  amounts  become  surprisingly  large.  Thus,  for  a  period 
of  a  year,  the  hen  produces  about  seventy-five  pounds,  the 
sheep  nearly  a  ton,  and  the  cow  fourteen  tons;  so  you  see 
that  the  manure  produced  on  a  farm  of  moderate  size  and 
supporting,  let  us  say,  twenty  cows  and  the  usual  amount 
of  other  live  stock,  amounts  to  several  hundred  tons  yearly. 
It  will  be  interesting  to  calculate  the  amount  for  your  own 
farm  per  year,  using  ten  and  fifty  pounds  for  the  daily  pro- 
duction of  the  pig  and  horse  respectively.  The  total  yearly 
production  of  the  United  States  is  enormous.  From  the 
latest  census  returns  from  all  classes  of  farm  animals,  it  has 
been  estimated  as  over  one  billion  tons.     At  the  standard 


238  CHEMISTRY  OF  THE  FARM  AND  HOME 

market  prices,  the  plant  food  of  a  ton  of  mixed  manure  is 
worth  $2.00;  hence  the  value  of  the  yearly  production  of 
our  country  must  be  over  two  billion  dollars.  As  we  shall 
see  later,  one  fourth  of  this  value,  and  perhaps  much  more, 
may  be  lost  by  carelessness.  Should  not  the  farmer  hus- 
band this  valuable  resource? 

The  amount  of  manure  produced  depends  upon  the 
amount  of  food  which  is  fed.  One  can  calculate  roughly 
the  amount  of  manure  produced  from  a  given  ration.  In 
the  first  place,  one  must  compute  the  amount  of  dry  matter 
fed.  It  is  necessary  to  regard  the  dry  matter,  because  the 
water  present  in  the  feeds  is  not  changed  in  quantity  by 
digestion,  while  the  dry  matter  is.  Now,  one  half  of  the 
dry  matter  on  the  average,  is  excreted  as  dry  matter  of  the 
manure.  The  other  half  is  either  used  in  building  the  body 
tissue  or  excreted  as  gases  and  water.  This  one  half  of 
the  dry  ration  will  be  increased  by  one  half  of  its  own  weight 
added  as  dry  matter  in  bedding.  Thus,  the  dry  matter 
of  the  manure  is  about  three  fourths  of  that  in  the  ration. 
Now  the  average  amount  of  water  in  mixed  farm  manure 
is  75  per  cent.  Putting  it  in  another  way,  the  fresh  ma- 
nure weighs  four  times  as  much  as  the  dry  matter  which 
it  contains.  Therefore,  if  this  dry  matter  is  three  fourths 
of  the  dry  matter  of  the  ration,  as  just  stated  the  fresh  ma- 
nure will  weigh  four  times  three  fourths  of  the  dry  matter  fed. 
Hence,  the  fresh  manure  will  weigh  three  times  as  much  as 
the  dry  ration.  Let  us  take  an  example  of  this  calculation. 
A  ration  contains  10  pounds  of  clover  hay  and  5  pounds  of 
wheat  bran.  The  clover  hay  contains  15  per  cent  of  water 
and  the  bran,  12  per  cent.  Therefore,  the  ration  contains  8.5 
pounds  of  dry  clover  and  4.4  pounds  of  dry  bran,  a  total  of 
12.9  pounds  of  dry  matter.  Thre^  fourths  of  this  value, 
which  is  the  sum  of  the  dry  matter  excreted  and  the  dry 
matter  of  bedding,  is  9.7  pounds.  The  fresh  manure  will 
weigh  four  times  this  amount,  or  38.8  pounds.     Can  you  not 


FARM  MANURE  239 

find  out  the  kind  and  amount  of  rations  fed  at  home  or  on 
some  neighbor's  farm  and  calculate  the  amount  of  manure  it 
should  produce?  You  may  need  to  consult  a  larger  text- 
book for  the  percentage  of  water  in  some  feeding  stuffs. 
The  value  of  fresh  manure  depends  chiefly  upon  the 
kind  of  feeding  stuffs  which  are  fed.  Like  any  other  pro- 
duct, it  can  be  of  no  higher  quality  than  the  materials  from 
which  it  is  made.  Farm  manure  is  either  rich  or  poor, 
dependent  on  whether  the  food  eaten  by  the  animals  is 
rich  or  poor  in  the  essential  elements.  This  is  especially 
true  of  nitrogen,  as  this  is  the  most  important  and  the 
most  expensive  of  the  essential  elements.  Thus,  a  ration 
containing  clover  hay,  which  contains  2.1  per  cent  of  nitro- 
gen, will  produce  richer  manure  than  one  containing  timo- 
thy hay,  which  contains  only  1.3  per  cent  of  nitrogen.* 
You  can  see  from  this  that  it  is  possible  to  increase  the 
value  of  the  manure  by  raising  and  feeding  leguminous 
crops.  What  practically  inexhaustible  storehouse  have  we 
already  learned  is  the  source  of  the  nitrogen  obtained  by 
these  crops?  Unfortunately,  there  is  no  such  source  avail- 
able for  either  phosphorus  or  potassium.  There  is  no  other 
reservoir  than  the  soil  itself  from  which  these  elements  can 
be  obtained  without  cost.  In  order  to  keep  the  soil  fertile, 
either  the  amounts  removed  by  crops  must  be  returned  to 
the  soil  without  loss  or  they  must  be  replaced  by  purchase 
from  outside  the  farm.  Potassium  can  be  obtained  as  a 
constituent  of  commercial  fertilizers.  Most  types  of  soil, 
however,  contain  large  amounts  of  it;  so  that  it  is  not  always 
necessary  to  buy  it.  Fortunately,  phosphorus,  the  most 
frequently  exhausted  of  -the  essential  elements,  can  be 
recovered  in  certain  by-products  of  crops.  This  element  is 
especially  important  in  grain  formation  and  accumulates 
in  many  seeds.  In  wheat  and  rice,  which  form  a  large 
proportion  of  the  common  grain  crops,  it  is  present  chiefly 
in   the   outer   husks,    which   form   the   bran.     Over   three 


240  CHEMISTRY  OF  THE  FARM  AND  HOME 

fourths  of  the  total  phosphorus  of  the  wheat  grain  is  re- 
moved with  the  bran.  It  is  thus  possible  for  the  farmer  to 
profit  in  fertilizing  by  purchasing  wheat  bran  to  offset  feed- 
ing stuffs  raised  on  his  farm.  For  example,  with  corn  at 
70  cents  per  bushel  and  wheat  bran  at  $28.00  per  ton,  one 
could  purchase  0.9  ton  of  bran  with  the  receipts  from  one 
ton,  or  35.7  bushels  of  corn.  The  exchange  would  result 
in  a  gain  of  over  16  pounds  of  phosphorus,  to  say  nothing  of 
large  gains  of  nitrogen  and  potassium.  With  the  market 
values  of  nitrogen,  potassium  and  phosphorus  at  15  cents, 
6  cents,  and  11  cents  per  pound,  respectively,  the  gain  of 
fertility  by  the  transaction  would  be  worth  over  $4.50.  It 
will  be  worth  while  to  calculate  the  gain  by  this  exchange 
at  present  prices,  also  the  gain  by  the  exchange  of  other 
crops  than  corn  for  the  wheat  bran.  If  the  tables  which 
you  consult  give  the  percentage  of  phosphoric  acid  (P2O5) 
in  feeding  stuffs,  multiply  it  by  0.44  to  convert  to  phos- 
phorus value.  Multiply  the  percentage  of  potash  (K2O) 
by  0.83  to  convert  it  to  its  potassium  equivalent. 

Manurial  Value  of  Feeding  Stuffs.  While  making  these 
computations  on  the  fertility  value  of  feeding  stuffs  we 
must  remember  that  not  all  this  plant  food  is  recovered 
in  the  manure.  The  animal  needs  some  of  the  elements 
for  his  own  growth  and  work.  The  greatest  needs  are  those 
of  the  growing  animal  and  the  mother  producing  milk. 
During  the  first  year  of  their  lives,  cattle  use  about  one 
fifth  of  the  nitrogen  and  phosphorus  of  their  food.  The 
nitrogen  is  required  for  making  muscle  and  the  phosphorus 
for  building  bone.  A  cow  in  full  milk  flow  uses  about  the 
same  proportion  of  these  elements  in  producing  milk.  A 
mature  working  horse,  on  the  other  hand,  uses  only  small 
amounts  of  these  elements  to  repair  the  waste  of  his  tissues; 
and  the  mature,  fattening  animal  retains  almost  no  fertility, 
because  he  is  doing  nothing  but  constructing  fat,  and  fat 
contains    no    nitrogen,    phosphorus    or    potassium.     It    is 


FARiM  MANURE  241. 

generally  considered  that  the  average  amount  of  fertility 
in  feeding  stuffs  returned  in  the  manure  by  all  kinds  of  farm 
animals  is  80  per  cent  of  the  total.  This  amount  is  called 
the  manurial  value,  in  distinction  from  the  fertility  value 
of  feeding  stuffs.  The  latter  is  the  full  value  of  the  plant 
food ;  the  former  of  what  is  excreted  in  the  manure. 

Manure  of  Different  Animals.  If  we  compare  the 
composition  of  the  fresh,  mixed  excrement  of  different 
animals,  we  shall  find  great  differences.  Sheep  manure, 
for  example,  contains  about  twice  as  much  nitrogen,  and 
one  half  more  phosphorus  and  potassium  than  cow  manure. 
This  apparently  great  difference  is  due  chiefly  to  the  dif- 
ferent amounts  of  water  in  the  fresh  manure.  Exclusive 
of  the  bedding,  cow  manure  contains  about  85  per  ceijt  of 
water,  horse  manure  70  per  cent,  sheep  manure  60  per  cent, 
and  hen  manure  only  55  per  cent.  So  you  see  that  from 
any  one  feeding  stuff  the  sheep  or  hen  will  produce  a  much 
more  concentrated  and  hence  richer  manure  than  the  cow. 
When  the  percentages  of  the  essential  elements  are  calcu- 
lated upon  the  dry  matter,  the  differences  are  far  less. 
The  chief  difference  is  that  sheep  and  hen  manures  are 
about  one  fourth  and  one  third  richer  in  nitrogen,  respec- 
tively, than  the  more  common  manures.  This  is  not  due 
to  any  peculiar  power  of  the  animal,  but  to  the  nature  of 
its  food,  and  the  uses  to  which  it  is  put. 

On  the  farm  one  deals  with  manure  containing  litter. 
We  ought,  therefore,  to  study  the  value  of  this  product, 
rather  than  of  the  freshly  dropped  excrement.  Fresh  cow 
manure  with  bedding  contains  on  the  average  0.5,  0.1,  and 
0.4  per  cent  of  nitrogen,  phosphorus  and  potassium.  You 
will  get  the  value  of  these  figures,  if  you  will  calculate  them 
to  pounds  per  ton  of  manure.  Mixed  farm  manure  con- 
tains about  one  fourth  more  nitrogen  and  potassium. 

Urine  Saved  by  Litter.  From  one  half  to  two  thirds 
of  the  nitrogen  and  potassium  are  excreted  in  the  urine. 

16— 


242 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Therefore,  just  that  part  of  the  manure  which  is  most  per- 
ishable contains  at  least  one  half  of  its  fertilizing  value.  Is 
not  the  great  value  of  the  urine  quite  clear? 

This  important  part  of  the  manure  can  be  saved  best 
by  keeping  the  animals  on  tight  floors  and  using  bedding 


Figure  66.      Manure  Spreader.     After  the  liquid  part  has  been  absorbed  with  bed- 
ding and  litter  the  manure  should  be  spread  upon  the  land  as  soon  as  possible. 

liberally.  Dry  peat  moss  is  an  excellent  absorbent  for  use 
as  bedding.  It  is  quite  as  absorbent  of  liquids  as  a  sponge. 
Straw,  leaves  and  other  common  bedding  materials  absorb 
much  more  water  when  finely  divided  than  when  in  coarse 
condition.  For  this  reason  it  pays  to  cut  straw  into  short 
lengths  for  bedding.  When  precautions  have  been  taken 
to  save  the  urine,  it  should  be  remembered  that  the  manure 
is  a  perishable  product.  Like  other  products  of  this  sort, 
it  should  be  gotten  to  the  consumer  as  soon  as  possible.  It 
should  be  hauled  to  the  field  and  spread  daily  as  it  is  pro- 
duced. In  this  way,  there  is  the  least  loss  of  fertility  and 
the  greatest  return  in  crops.  Such  results  repay  many 
fold  the  original  cost  of  a  manure  spreader. 


FARM  MANURE 


243 


Losses  in  Stored  Manure.  When  not  spread  directly, 
manure  is  liable  to  serious  loss  of  value  in  two  ways.  In  the 
first  place,  when  it  is  rather  dry  and  loose,  as  is  horse 
manure,  it  is  vigorously  attacked  by  bacteria.  The  changes 
which  go  on  are  spoken  of  collectively  as  ''fermentation." 
They  are  due  to  chemical  reaction  fet  up  by  enzyme- 
secreted  by  the 
bacteria.  Two 
reactions  pro 
ceed  rapidly. 

First :  oxida- 
tion, favored  by 
the  free  supply- 
ing of  air,  de- 
stroys much    of 

Figure  67.     A  cart  used  in  Switzerland  for  taking  liquid      the  Organic  mat- 
manure  to  the  field. 

ter.  In  what 
compounds  will  carbon  and  hydrogen  be  lost?  Nitrogen  will 
be  lost  as  a  constituent  of  ammonia  NH3.  This  process  gen- 
erates much  heat,  so  that  the  temperature  of  the  interior 
of  a  pile  of  horse  manure  may  reach  even  80°C. 

Second:  hydrolysis  causes  rapid  loss  of  ammonia  from 
fermenting  manure.  This  is  the  kind  of  chemical  change 
in  which  water  is  caused  to  combine  with  other  compounds 
and  to  produce  new  and  simpler  compounds.  The  great- 
est loss  is  due  to  the  union  of  water  with  urea,  an  important 
nitrogenous  compound  of  the  urine.  Urea  is  an  amide. 
By  combining  with  water  in  the  proportion  of  one  part  to 
two  parts,  respectively,  it  yields  ammonium  carbonate. 
This  salt,  as  you  can  easily  prove  by  smelling  a  lump  of  it, 
decomposes  at  ordinary  room  temperature.  At  the  higher 
temperatures  of  the  fermenting  manure,  it  decomposes 
rapidly  into  ammonia,  carbon  dioxide  and  water.  Have 
you  not  noticed  the  peculiar  odor  prevalent  about  horse 
stables  in  warm  weather?    This  odor  sometimes    becomes 


244 


Chemistry  of  the  farm  and  home 


fairly  stifling  when  one  forks  the  manure  pile  open.  It  is 
due  to  escaping  ammonia.  One  fourth  to  three  fourths  of 
the  valuable  nitrogen  of  the  manure  may  be  lost  in  this 
manner. 

A  second  serious  loss  occurs  when  manure  is  exposed 
to  the  rain.  Where  the  rain  falls  on  shallow,  loose  piles 
it  washes  or  leaches  the  soluble  constituents  .from  the  ma- 
ure.  Thus,  while  only  nitrogen  is  lost  by  fermentation, 
leaching  removes  potassium  and  phosphorus  also.  Worst 
of  all,  it  removes  just  those  compounds  which  are  most 
soluble  and  available  for  use  by  the  crops.  The  residue 
from  leaching,  even  by  short  rains,  has  but  one  half  or  less 
of  the  crop-producing  power  of  unleached  manure.  Know- 
ing these  facts,  one  can  realize  the  great  value  of  the  dark 
liquid  often  allowed  to  ooze  away  from  the  manure  piles. 

Spreading  the  Manure.  The  statements  just  made 
emphasize  the  importance  of  spreading  the  fresh  manure 

directly  upon 
the  land.  To 
leave  the  manure 
in  piles  in  the 
field  is  nearly  as 
wasteful  as  to 
allow  it  to  accu- 
mulate at  the 
barnyard.  In 
this  way,  the 
plant  food  leach- 
es into  spots  and 
most  of  the  field 
fails  to  receive 
much  of  the  benefit  from  manuring.  Of  course,  one  should 
avoid  spreading  the  manure  on  steep  slopes  without  promptly 
working  it  into  the  soil,  as  it  is  very  likely  to  be  washed 
away  by  rain. 


Figure  68.  A  properly  made  manure  pile.  It  should 
be  built  high  with  nearly  vertical  sides  and  a 
depressed  center. 


FARM  manure:  245 

The  Manure  Pile.  When  the  manure  must  be  kept 
until  such  times  as  it  can  be  hauled  to  the  fields,  it  should 
be  piled  with  care.  The  pile  should  be  made  round  with 
nearly  vertical  sides  and  dished  at  the  top,  as  shown  in 
Figure  68.  Such  a  shape  throws  the  rainfall  into  the  center 
of  the  pile  and  prevents  loss  by  leaching.  Compacting  the 
pile  by  treading  as  the  manure  is  added  reduces  the  air 
spaces  and  checks  fermentation.  Mixing  the  ''hot  horse 
manure"  with  the  "cold  cow  manure"  also  reduces  fer- 
mentation. The  presence  of  a  large  amount  of  water 
is  both  unfavorable  to  the  oxidizing  bacteria,  and  also 
absorbs  much  heat,  keeping  the  mass  cold.  Addition  of 
water  to  the  pile,  by  rain  or  otherwise,  has  the  same  effect. 
Such  treatment  does  not  entirely  prevent  the  loss  of  fertility, 
as  chemical  changes  are  produced  by  the  action  of  bacteria 
which  thrive  without  oxygen.  Yet  the  loss  of  nitrogen 
can  be  reduced  to  only  one  tenth  of  the  total,  whereas 
three  fourths  is  often  lost  from  poorly  kept  manure. 

Absorbents  and  Preservatives.  Sometimes  the  farmer 
tries  to  "lock  the  stable  after  the  horse  is  stolen"  by 
preventing  the  loss  of  ammonia  set  free  by  fermentation. 
This  is  done  by  sprinkling  the  manure  with  materials  which 
retain  the  ammonia.  These  materials  act  either  by  absorb- 
ing ammonia  physically  or  by  reacting  with  it  chemically. 
Dry  peat  and  muck  are  good  for  the  purpose,  as  they  absorb 
large  volumes  of  gases  mechanically,  just  as  does  charcoal. 
The  use  of  much  of  these  materials  in  piled  manure  must 
be  avoided,  as  they  dry  the  manure  and  increase  fermenta- 
tion. Among  the  chemical  preservatives,  gypsum  or  land 
plaster  has  been  commonly  used.  Its  action  depends  on 
the  fact  that  calcium  sulphate  reacts  with  ammonium  car- 
bonate to  form  calcium  carbonate  and  ammonium  sul- 
phate. In  contrast  to  ammonium  carbonate  the  sulphate 
is  not  volatile  and  subject  to  loss.  The  process  is  not 
efficient,  however,  as  it  requires  a  large  excess  of  gypsum 


246 


CHEMISTRY  OF  THE  FARM  AND  HOME 


to  produce  the  change.  Any  acid  material,  such  as  acid 
phosphate  fertihzer,  will  combine  with  ammonia.  You 
will  see  that  this  reaction  is  of  a  much  simpler  kind  than  in 
the  case  of  gypsum.  These  materials  should  be  added  to 
the  manure  as  it  is  taken  from  the  stable,  for  they  are  in- 
jurious to  the  feet  of  animals.  Contrary  to  a  common 
belief,  ''floats"  or  finely  ground  rock  phosphate  has  no  power 
to  retain  ammonia.  The  practice  of  adding  either  ashes 
or  lime  to  manure  in  the  barn  as  a  "sweetener''  is  a  very 
serious  error.  These  materials  should  never  be  added  to 
the  manure,  excepting  when  the  latter  is  to  be  worked  into 
the  soil  immediately.  They  are  strong  alkalies  which 
displace  ammonia  from  its  compounds  and  set  it  free. 

Increasing  the  Value  of  Manure.  The  farmer  should 
aim  to  increase  the  value  of  his  manure.  As  already  shown, 
this  can  be  done  by  the  purchase  of  certain  feeding  stuffs. 
On  farms  which  do  not  consume  wheat  bran  and  similar 
commercial  feeding  stuffs  certain  commercial  fertilizing 
materials  may  be  purchased  for  reinforcing  the  manure. 
The  most  common  of  these  for  supplying  phosphorus  are 
rock  phosphate  and  acid  phosphate.  They  are  usually  add- 
ed at  the  rate  of  forty  pounds  per  ton  of  manure,  sprinkled 

over  successive 
layers  of  manure 
as  the  spreader 
is  loaded.  For- 
merly it  was  be- 
lieved that  car- 
bonic acid  and 
other  organic 
acids  formed  in 
the  fermenting 
manure  produc- 
ed soluble  com- 

Figure  69.     Mixing  phosphorus  and  potassium  fertilizers  i         f      U 

with  the  manure  to  increase  its  effect.  pOUnOS    01  pnOS- 


FARM  MANURE  247 

phorus  from  the  insoluble  rock  phosphate.  Now  we  know 
that  this  change  does  not  occur  in  the  manure  pile,  but  in 
the  soil.  Many  years  of  study  at  the  Ohio  Experiment 
Station  have  shown  that  the  net  returns  from  using  acid 
phosphate  are  greater  than  those  from  rock  phosphate. 
When  the  soil  needs  potassium,  it  is  best  to  reinforce 
the  manure  with  one  of  the  high-grade  potassium 
salts  about  which  we  learned  in  the  chapter  on  fertilizers. 

Use  of  Manure.  Proper  use  of  manure  requires  atten- 
tion to  certain  scientific  principles.  Two  important  effects 
produced  by  it  should  be  kept  in  mind:  (1)  it  increases 
the  supply  of  plant  food;  and  (2)  it  increases  the  supply  of 
humus.  In  order  to  produce  either  of  these  effects  it  must 
decay  freely.  If  conditions  do  not  favor  its  decay,  uncom- 
mon compounds,  poisonous  to  plants,  may  be  produced. 
What  is  the  chief  chemical  change  which  causes  the  decay- 
ing of  manure,  either  in  loose  piles  or  when  mixed  with  the 
soil?  Would  you  expect  oxidation  to  proceed  favorably 
in  manure  buried  a  foot  beneath  the  surface  of  the  soil? 
Favorable  oxidation  of  the  material  is  best  favored  by  only 
moderate  applications.  Eight  tons  per  acre  is  a  good  amount 
to  use,  applying  it  to  the  tilled  crop  of  the  crop  rotation. 
On  heavy  clay  soils  which  exclude  the  air  it  should  not  be 
plowed  deeper  than  four  inches,  but  upon  sandy  soils  it 
may  be  covered  deeper.  Can  you  see  any  reason  why 
shallow  covering  of  the  manure  and  tilling  of  the  soil  have 
a  favorable  effect  on  the  decomposition  of  the  manure? 
A  further  reason  for  desiring  the  favorable  oxidation  of  the 
manure  is  that  it  warms  the  soil.  Manured  soils  are  always 
1°  to  2°C.  warmer  than  unmanured  soils  in  the  summer 
season,  when  bacteria  are  destroying  the  organic  matter. 

Rotten  manure  is  better  than  fresh  manure  for  some 
purposes,  especially  for  light,  sandy  soils,  whose  unfavorable 
porous  conditions  would  be  increased  by  coarse,  fresh  man- 
ure; and  for  some  uses  in  the  greenhouse.    The  fresh  and  rot- 


248  CHEMISTRY  OF  THE  FARM  AND  HOME 

ted  manure  are  equally  efficient,  ton  for  ton;  but  it  takes 
two  tons  of  the  former  to  make  a  ton  of  the  latter;  so  the 
rotting  process  involves  much  loss.  The  process  is  carried 
out  by  composting  or  packing  in  a  compact  heap.  Waste 
plant  and  animal  matter  may  be  added  and  soil  is  mixed 
into  the  heap.  The  pile  is  forked  over  occasionally  and 
enough  water  added  to  promote  oxidation.  There  is  un- 
avoidable loss  of  nitrogen  in  the  process.  Such  treatment 
has  the  favorable  effect,  however,  of  killing  weed  seeds. 

Excessive  manuring  sometimes  causes  lodging  of  grain 
crops  such  as  oats.  This  is  due  to  the  production  of  an 
excess  of  nitrates,  which  produce  a  heavy  growth  of  foliage. 
The  heavy  shade  so  weakens  the  stems  that  they  break 
in  the  stress  of  a  beating  rain.  A  few  tilled  crops  profit  by 
heavy  manuring.  Fourteen  tons  per  acre  is  a  favorable 
application  for  the  heavy-feeding  mangel.  It  is  good  prac- 
tice to  spread  manure  on  grass  sod  in  the  fall.  In  this  way 
the  period  of  nitrification  is  lengthened  without  loss  of 
nitrates  by  leaching,  as  the  growing  crop  assimilates  them. 

The  effects  of  manure  are  quite  different  from  those  of 
commercial  fertilizers.  While  the  latter  must  be  used  con- 
tinuously, the  former  produces  favorable  effects  which 
increase  the  yield  of  crops  for  many  years  after  its  use. 

The  place  of  manure  in  keeping  up  the  fertility  of  the 
soil  has  been  studied  for  many  years  at  the  Ohio  Experi- 
ment Station.  It  is  the  practice  of  many  farm  tenants 
to  omit  the  use  of  any  sort  of  fertilizer  for  fear  that  others 
will  profit  from  their  investments.  The  Ohio  experiments 
show  that  this  is  the  poorest  sort  of  management.  On  a 
160  acre  farm  with  soil  in  rundown  condition,  an  unmanured 
three-course  rotation  of  corn,  wheat  and  clover  will  net  the 
farmer  about  $400.00.  The  appHcation  of  eight  tons  of 
manure  per  acre  to  his  corn  will  give  a  net  profit  of  $1200.00. 
Still  further,  the  use  of  acid  phosphate  with  the  manure 
will  increase  the  profit  to  $1,800.00.     Can  any  more  strik- 


FARM  MANURE  249 

ing  evidence  be  needed  to  show  the  value  of  manure  and 
the  importance  of  supplementing  it  with  commercial  fertili- 
zers? The  purchase  of  ten  tons  of  wheat  bran  yearly  on 
such  a  farm  will  replace  the  phosphorus  and  potassium  sold 
in  its  products.  Indeed,  a  well-managed  stock  or  dairy 
farm  actually  increases  in  fertility. 

Green  manuring  is  the  process  of  increasing  soft  humus 
and  available  plant  food  by  ploughing  green  crops  directly 
back  into  the  soil.  Sometimes  grains  or  grasses  are  grown 
in  the  fall  after  tilled  crops  and  treated  in  this  way.  So 
used,  they  save  nitrates  from  leaching  and  are  called  ''catch 
crops."  Clover,  soy  beans  and  other  legumes  are  far  better 
green  manures  than  the  common  grasses,  because  they  en- 
rich the  soil  in  nitrogen.  A  better  common  practice  than 
green-manuring,  however,  is  to  feed  these  crops  and  carefully 
use  the  manure.     In  this  way,  they  serve  double  usefulness. 

Sewage.  Human  excrement  is  a  fertilizing  material 
whose  loss  forms  one  of  the  extravagant  features  of  civili- 
zation. With  the  dry,  earth  closet,  still  common  to  country 
homes  and  villages,  it  is  possible  to  return  the  plant  food  of 
this  material  to  the  soil.  In  cities,  however,  its  accum- 
ulation becomes  both  a  nuisance  and  a  menace  to  health. 
This  condition  led  to  the  present  method  of  flushing  excreta 
away  with  a  large  volume  of  water.  Attempts  have  been 
made  both  to  evaporate  the  water  from  the  greatly  diluted 
sewage  and  to  precipate  the  suspended  matter.  None 
of  these  methods  have  yet  proved  practical.  Some  cities 
have  experimented  with  filter  beds  of  sandy  soil  upon 
which  truck  crops  can  be  grown.  Even  this  has  not  been 
found  feasible  for  general  use. 

Our  present  wasteful  practice  is  a  great  contrast  to  the 
methods  of  the  Chinese  and  Japanese  for  saving  human 
excrement.  Figure  70  shows  how  extensive  is  the  business 
of  saving  this  material  in  a  great  city  of  China.  Such  a 
method  is  possible,  of  course,  only  in  countries  where  labor 


250 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Figure  70.     Collecting  human  manure  from  the  city  of  Shanghai,  China. 
From  King's  "Farmera  of  Forty  Centuries,"  by  permission  of  Mrs.  F.  H.  King. 

is  cheap  and  the  problem  of  growing  food  plants  is  acute. 
With  continued  increase  of  population  in  our  country 
there  must  come,  eventually,  a  shortage  of  commercial 
fertilizers  and  farm  manure.  Such  a  condition  will  neces- 
sitate the  invention  of  practical  methods  for  saving  the 
enormous  quantity  of  plant  food  now  lost  in  sewage. 


SUMMARY 

Farm  manure  is  a  stage  in  the  cycle  of  elements  from  the  air  and 
soil  through  plants  and  animals.  That  portion  of  essential  elements 
contained  in  the  liquid  part  of  the  manure  is  in  an  available  and  very 
valuable  form,  and  should  be  saved  by  liberal  use  of  bedding. 

The  amount  of  manure  depends  upon  the  amount  of  feeding  stuffs 
fed.  Its  composition  and  value,  when  fresh,  depend  upon  the  com- 
position of  the  feeding  stuffs.  After  the  requirements  of  growth  and 
milk  production  are  satisfied,  animals  excrete  about  four  fifths  of  the 
essential  elements  of  the  feeding  stuffs.  By  selecting  certain  feeding 
stuffs  the  farmer  can  increase  the  value  of  his  manure. 

Some  manures  are  much  drier  than  others  and  ferment  rapidly, 
on  account  of  bacterial  action.  Fermentation  causes  much  loss  of 
nitrogen  from  the  liquid  portion.     The  latter  is  also  subject  to  heavy 


FARM  MANURE  251 

loss  by  leaching  due  to  rain.  To  avoid  these  losses,  manure  should  be 
spread  on  the  land  as  fast  as  it  is  produced.  When  it  can  not  be  thus 
spread  the  wet  and  dry  manures  should  be  mixed  in  a  compact  pile. 
Commercial  fertilizers  can  be  mixed  with  it  to  increase  its  value. 

In  order  that  oxidation,  by  which  manure  is  made  useful,  may 
proceed  freely  the  material  should  be  apphed  to  tilled  crops  and  not 
covered  deeply.  When  so  used  it  produces  lasting  effects.  Its  use  in 
a  three-crop  rotation  will  triple  the  farmer's  net  profits. 

Green  manuring,  or  ploughing  crops  under  for  fertilizer,  is  a  val- 
uable practice  where  the  crops  are  legumes.  It  is  a  less  desirable  prac- 
tice than  the  combination  of  feeding  the  crops  with  saving  of  the  manure. 

In  contrast  to  the  careful  use  of  human  excrement  in  Oriental 
countries,  our  city  sewage  systems  cause  enormous  losses  of  plant  food. 
Increasmg  population  may  cause  this  waste  to  become  a  serious  prob- 
lem pressing  chemists  and  engineers  for  solution. 

QUESTIONS 

1.  Why  is  farm  manure  the  most  generally  useful  fertilizer? 

2.  Which  is  the  more  valuable  per  pound,  dung  or  urine?    Why? 

3.  What  is  the  approximate  value  of  the  farm  manure  produced 
annually  in  our  country? 

4.  How  can  amount  of  manure  be  computed  from  the  ration  fed? 

5.  Upon  what  factor  does  the  value  of  fresh  manure  chiefly 
depend? 

6.  How  can  one  increase  the  amount  of  nitrogen  in  the  manure? 
Of  phosphorus? 

7.  Does  all  the  plant  food  of  the  ration  reach  the  manure?  Why? 

8.  What  is  the  manurial  value  of  a  feeding  stuff? 

9.  Why  is  loss  of  the  urine  wasteful?     How  can  it  be  avoided? 

10.  What  two  serious  losses  may  occur  from  piled  manure? 
How  can  they  be  reduced? 

11.  How  would  you  proceed  to  reinforce  the  manure  with  either 
phosphorus  or  potassium? 

12.  What  are  the  objections  to  ploughing  manure  in  deeply? 

13.  For  what  purposes  is  rotten  manure  preferable  to  fresh  manure? 

14.  Why  should  heavy  applications  of  manure  be  avoided  with 
grain  crops? 

15.  What  was  the  difference  in  income  from  no  manure  and 
from  manure  with  acid  phosphate  in  the  Ohio  experiments? 

16.  What  is  the  purpose  of  green  manuring  "catch  crops"? 

17.  Would  you  advise  green  manuring  clover  on  a  stock  farm? 
Why? 

18.  What  objection  would  you  raise  to  the  present  method  of 
disposal  of  city  sewage? 


CHAPTER  X 
THE  ANIMAL  AND  ITS  PRODUCTS 

The  Animal  Body  a  Factory.  Can  you  think  of  your 
pet  dog,  with  all  his  intelligence  and  devotion,  as  a  machine? 
Perhaps  you  will  find  it  easier  to  think  in  this  way  of  your 
favorite  cow,  producing  nutritious  milk.  She  seems  to  put 
out  a  definite  product,  much  after  the  manner  of  a  machine  or 
a  factory.  In  reality,  the  live  bodies  of  all  animals  are 
machines.  Indeed,  they  are  even  factories,  requiring  only 
foods  as  raw  materials  and  fuel  to  turn  out  each  its  partic- 
ular product. 

The  work  of  various  animals,  whether  it  be  the  swift 
movements  of  the  winning  race-horse  or  the  butter -fat 
production  of  the  champion  dairy  cow,  is  done  at  the  expense 
of  energy  locked  up  in  compounds  of  their  feeding  stuffs. 
Their  products  also,  whether  they  be  the  flesh  of  prize  fat 
steers  or  the  eggs  of  prolific  hens,  are  made  by  reconstruc- 
tive chemical  processes  from  compounds  of  their  feeding 
stuffs.  Thus  we  see  that,  in  a  broad  sense,  the  body  of  a 
living  animal  is  a  sort  of  self-operating,  self -repairing  factory. 
In  addition  to  supplying  raw  material  for  making  the  prod- 
ucts of  this  factory,  food  supplies  it,  as  we  shall  see  later, 
with  power  and  heat  resulting  from  oxidation. 

The  place  of  the  animal  in  agriculture,  then,  closely 
resembles  that  of  a  machine  or  factory  in  other  industries. 
From  the  compounds  of  the  plant  as  raw  material  it  pro- 
duces power  and  special  finished  products  for  the  use  of 
man.  Some  of  these  products  we  shall  study  as  cloth  fibers, 
others  as  food  stuffs.  Let  us  now  inquire  further  into  the 
nature  and  mechanism  of  this  living  machine. 

Chief  Parts  of  the  Body.  In  general,  the  animal  body 
may  be  considered  in  four  chief  parts.     These  are:  the  skel- 

252 


The  animal  and  its  products  253 

eton,  the  vital  organs,  the  muscles,  and  the  skin.  The 
actions  of  all  these  parts  are  harmonized  by  the  nerves. 
Their  chemical  processes  are  linked  together  through  the 
blood   and  its   circulation. 

The  bony  skeleton  supports  the  body,  forms  leverage 
for  the  muscles  and  protects  the  vital  organs.  Bones 
consist  of  a  spongy  mold  of  protein  compounds,  chiefly 
ossein,  filled  with  calcium  phosphate  and  small  amounts  of 
other  salts.  Magnesium,  fluorine,  and  chlorine  are  present 
in  small  amounts.  The  central  marrow  and  soft  bony  tissues 
are  permeated  by  blood  and  Ij^mph  vessels  and  nerves. 
When  burned,  bones  leave  from  one  third  to  one  half  their 
weight  as  ash,  which  is  nearly  nine  tenths  tri calcium  phos- 
phate. 

The  vital  organs  include  the  brain,  heart,  lungs  and  the 
several  organs  of  digestion.  The  tissues  from  which  they 
are  formed  consist  principally  of  protein  compounds.  In- 
deed, these  compounds  furnish  the  chief  material  from  which 
is  constructed  the  framework  of  every  individual  cell  of  the 
animal  body.  There  is  in  animals  no  special  cell-wall 
compound  like  cellulose  of  plants.  The  protein  frame  work 
of  some  cells  may  be  more  or  less  filled  with  fats. 

Muscles  are  the  chief  organs  in  which  occur  the  reactions 
of  oxidation  which  provide  the  body  with  heat  and  energy, 
or  power.  It  is  heat  provided  in  this  way  which  keeps 
the  bodies  of  common  animals  at  a  temperature  of  98°  to 
100°  Fahrenheit,  even  during  cold  weather.  The  muscles 
are  attached  by  both  ends  to  the  bones,  so  that  their  con- 
tractions move  the  various  parts  of  the  body.  They  also 
round  out  and  give  form  to  the  body.  They  are  composed 
of  a  tissue  of  protein  compounds  bathed  by  a  fluid  contain- 
ing dextrose,  salts  and  other  compounds. 

The  skin  is  primarily  an  organ  of  protection.  Hair, 
nail,  horn  and  hoof  are  special  outgrowths  from  it.  Carti- 
lage and  tendon  are  related  to  it.     These  tissues  are  all 


254  CHEMISTRY  OF   THE  FARM  AND  HOME 

composed  of  modified  forms  of  protein  compounds.  The 
elasticity  of  the  skin  is  due  to  elastin.  In  cartilage,  or 
gristle,  the  chief  compound  is  collagen.  By  soaking  bones 
in  hot  water  the  collagen  of  the  cartilage  and  tendons  is 
made  soluble.  On  cooling  the  extract,  gelatin  solidifies 
from  it.  This  compound  is,  as  you  know,  much  used  for 
making  jelly-like  desserts.  It  contains  about  0.6  per  cent 
of  sulphur.  The  chief  compound  of  hair,  wool,  feathers, 
hoof,  horn  and  related  tissues  is  keratin.  This  protein  is 
so  severely  modified  from  the  simple  form  that  it  is  much 
more  resistant  than  even  collagen.  It  becomes  soluble, 
however,  by  heating  with  steam  under  pressure  and  forms 
glue.  Keratin  is  much  richer  in  sulphur  than  common 
proteins.  It  contains  four  or  five  per  cent  of  the  element. 
All  these  compounds  related  to  the  skin  are  very  resistant 
and  durable  and  well  suited  to  their  duties  of  protection. 

Blood  consists  of  a  liquid  part,  the  plasma,  in  which  are 
suspended  a  great  many  discs  of  microscopic  size.  These 
discs  are  the  red  and  white  corpuscles.  They  form  about 
one  third  of  the  total  bulk  of  the  blood,  the  red  ones  producing 
the  characteristic  scarlet  color.  Have  you  ever  observed 
carefully  the  clotting  of  blood  soon  after  it  comes  from  the 
body?  The  dark  red  clot  is  formed  by  corpuscles  entangled 
in  threads  of  a  protein  called  fibrin  which  gradually  separates 
from  the  liquid.  Calcium  salts  play  an  important  part  in 
this  process.  The  clot  is  not  the  only  product  resulting 
from  the  process,  however.  It  is  surrounded  by  a  yellowish 
liquid,  the  serum.  This  part  of  the  blood  is  now  much  used 
in  bacteriological  and  medical  work,  as  in  treating  hog 
cholera.  In  chemical  composition  the  blood  consists  of 
about  four  fifths  water.  Of  the  remaining  solid  part,  over 
three  fourths  is  protein  compounds.  The  most  abundant 
of  these  compounds  is  haemo-globin,  which  gives  the  red 
color  to  the  blood.  This  compound  contains  about  one 
half  of  one  per  cent  of  iron,  to  which  it  seems  to  owe  its  power 


THE  ANIMAL  AND  ITS  PRODUCTS  255 

to  combine  with  oxygen.  It  unites  with  oxygen  to  form 
oxyhaemo-globin,  changing  from  purple  to  scarlet  in  color. 
The  blood  contains  small  amounts  of  proteins  and  related 
compounds  moving  either  to  the  tissues  as  food  or  to  the 
excretory  organs  as  waste  products.  It  also  contains  a  few 
tenths  of  one  per  cent  of  dextrose,  and  fatty  compounds  and 
ash-forming  elements.  Sodium  chloride  forms  the  greater 
part  of  the  ash.  Lymph  closely  resembles  blood  plasma 
in  composition.  There  is  much  more  fat  in  it,  however, 
suspended  in  minute  globules,  which  gives  it  a  milky  ap- 
pearance. It  serves  as  a  medium  through  which  compounds 
are  exchanged  between  the  blood  and  the  tissues. 

Nerves  include  a  central  mass  of  tissue  known  as  the 
brain  of  higher  animals.  They  differ  distinctively  from 
the  other  tissues  we  have  studied  by  containing  considerable 
amounts  of  nucleo-proteins.  These  compounds  are  complex 
combinations  of  proteins  with  organic,  phosphorus-contain- 
ing groups,  the  nucleic  acids.  They  contain  0.5  to  1.5  per 
cent  of  phosphorus.  Nucleo-proteins  are  most  character- 
istic and  abundant  in  those  cells  which  bear  the  burden  of 
reproduction.  This  fact  shows  how  very  important  phos- 
phorus   is    in    life   processes. 

The  composition  of  the  bodies  of  animals  has  been 
carefully  determined.  Whole  carcasses  of  steers  and  pigs 
have  been  analyzed  for  this  purpose.  These  analyses  have 
included  both  the  most  important  compounds  and  the  most 
abundant  elements.  All  material  in  the  digestive  organs  was 
removed  before  analyzing  the  bodies.  From  this  work  we 
learn  the  interesting  fact  that  the  body  of  a  lean  ox  is  two 
thirds  water.  Of  the  remaining  solid  matter  over  one  half 
is  protein,  about  one  fourth  is  fat,  and  one  fifth  is  ash  forming 
elements.  In  a  very  fat  ox,  on  the  other  hand,  water  forms 
but  about  one  half  the  total  bulk,  while  fat  forms  nearly  one 
third  of  it.  Of  the  solids  in  such  an  animal  fat  forms  six 
tenths,  protein  three  tenths,  and  ash  about  one  twelfth. 


256  CHEMISTRY  OF  THE  FARM  AND  HOME 

We  can  see,  then,  that  the  chief  difference  between  fat  and 
lean  animals  is  that  the  former  contains  more  fat  but  less 
water  than  the  latter.  What,  then,  is  the  nature  of  the 
fattening  process?  It  is  the  building  of  body  tissues  richer 
in  fat  and  poorer  in  other  compounds  than  usual.  Such 
fatty  tissue  is  about  two  thirds  fat,  and  one  fourth  water, 
with  small  amounts  of  protein  and  ash-forming  elements. 
These  differences  of  composition  are  as  true  for  the  pig 
or  any  other  animal  as  for  the  ox. 

The  elementary  composition  of  the  body,  that  is,  its 
percentages  of  different  chemical  elements,  is  shown  by  the 
following  interesting  data  for  man  given  by  Professor 
Kahlenberg  of  the  University  of  Wisconsin. 

Table  VIII. — Average  Elementary  Composition  of  the  Human  Body 

Per  Cent 

Oxygen 66.0 

Carbon 17.6 

Hydrogen 10.1 

Nitrogen 2.5 

Calcium 1.5 

Phosphorus 1.0 

Potassium 0.4 

Sodium 0.3 

Chlorine 0.3 

Sulphur • 0.25 

Magnesium 0.04 

Iron 0.004 

Sihcon,  Fluorine,  Iodine,  etc 0.006 

100.000 
We  ought  to  make  a  brief  survey  of  the  meaning  of  the 
figures  in  this  table.  Oxygen  and  hydrogen,  which  together 
form  over  three  fourths  of  the  body,  exist  chiefly  as  constitu- 
ents of  water;  but  they  are  also  abundant  in  the  fats,  pro- 
teins and  other  organic  compounds.  Carbon,  which  forms 
over  one  sixth  of  the  body,  by  weight,  is  the  keystone  ele- 
ment of  the  organic  compounds.  Nitrogen  and  sulphur, 
though  forming  but  a  small  part  of  the  body,  are  necessary 
constituents  of  the  very  important  protein  compounds. 
Phosphorus  occurs  in  nucleo-proteins,  the  calcium  phosphate 


THE  ANIMAL  AND  IT8  PRODUCTS  257 

of  bone  and  soluble  phosphates  of  the  tissue  fluids.  Potas- 
sium and  calcium  exist  chiefly  as  phosphates,  the  former  in 
fluids  and  the  latter  in  bone.  Sodium  and  chlorine,  com- 
bined in  sodium  chloride,  occur  in  the  gastric  juice  of  the 
stomach,  in  blood,  and  in  other  body  fluids.  Chlorine  also 
occurs  in  hydrochloric  acid  of  the  gastric  juice.  Magnesium 
is  present  in  salts  of  the  body  fluids  and  in  bone.  Iron  is 
a  part  of  the  molecule  of  haemo-globin  of  red  blood  corpus- 
cles. Silicon  occurs  in  very  small  amounts  in  hair  and 
feathers,  and  fluorine  in  bones. 

It  is  well-nigh  impossible  to  realize  completely  the  great 
importance  of  oxygen  to  the  body.  As  we  shall  see  later, 
it  enters  into  reactions  at  the  very  heart  of  life's  processes. 
The  importance  of  chemical  elements  in  the  body  is  not 
measured,  however,  by  their  amounts.  In  the  long  run, 
chlorine  is  quite  as  necessary  as  oxygen,  though  but  one 
two  hundred  and  twentieth  as  much  is  contained  in  the 
body.  Moreover,  iron  is  quite  as  essential  as  nitrogen, 
although  there  is  less  than  one  six-hundredth  as  much  of 
the  former  as  of  the  latter  in  the  body.  You  can  see  that 
chlorine,  apparently  unessential  to  plants,  takes  a  very 
definite  place  among  the  elements  essential  to  animal  life. 

Comparison  of  Young  and  Mature  Animals.  A  com- 
parison of  the  composition  of  mature  animals  with  that  of 
young  growing  animals  will  show  the  nature  of  the  tissues 
built  during  growth.  For  this  purpose,  we  may  choose 
cattle  quite  as  well  as  any  other  animal.  With  the  contents 
of  the  digestive  tract  removed,  the  fat  calf  consists  of  about 
65  per  cent  water,  16.5  per  cent  protein,  14  per  cent  fat  and 
5  per  cent  ash.  The  fat  ox  contains  only  50  per  cent  of 
water,  but  30.5  per  cent  of  fat,  with  about  one  per  cent  less 
protein  and  one  half  of  one  per  cent  less  ash  than  the  calf. 
This  comparison  shows  that  the  growing  animal  produces 
tissue  of  protein  nature,  or  lean  meat,  while  the  mature 
animal  lays  on  fat.     So,  the  composition  of  lean  animals  is 

17— 


258  CHEMISTRY  OF  THE  FARM  AND  HOME 

about  the  same  at  all  ages.  The  tissue  made  during  growth 
contains  about  twice  as  much  protein  as  fat,  the  two  classes 
of  compounds  forming  about  three  tenths  of  the  body  weight. 

The  proportions  of  those  chemical  elements  most  im- 
portant in  keeping  up  the  fertility  of  the  land  are  nearly 
the  same  in  young  and  mature  animals.  Nitrogen  forms, 
on  the  average,  about  2.5  per  cent  of  the  body,  phosphorus 
0.7  per  cent,  potassium  1.5  per  cent,  and  calcium  1.2  per 
cent.  The  pig,  however,  contains  less  of  these  elements 
than  the  other  animals  on  account  of  the  relative  smallness 
of  his  bones  and  his  greater  tendency  to  fatten.  From  this 
fact,  we  see  that  the  amounts  of  nitrogen  and  of  ash-form- 
ing constituents  depend  chiefly  upon  the  proportions  of  lean, 
protein  tissue  and  of  bony  skeleton  respectively.  The  fact 
that  young  and  mature  animals  have  practically  the  same 
composition  shows  that  tissue  of  nearly  constant  composition 
is  constructed  as  the  animal  grows. 

The  nutrition  of  the  animal  includes  those  processes  by 
which  growth  is  produced  and  the  various  tissues  of  the 
body  are  kept  in  repair.  It  embraces  a  complex  series  of 
chemical  and  physical  reactions.  There  are  four  chief 
groups  of  the  processes  of  nutrition,  which  succeed  one 
another  in  the  order  named :  Digestion,  absorption,  assimila- 
tion, excretion.  Digestion  includes  those  processes  by  which 
food  is  made  ready  for  the  cells  of  the  body.  Absorption 
includes  the  carrying  of  food  to  the  cells.  Assimilation 
covers  the  using  of  the  food  by  the  cells.  Excretion  removes 
unused  food  material  and  waste  products  of  assimilation 
from  the  cells  and  the  body.  We  shall  now  study  these 
divisions  of  nutrition  separately. 

Digestion  begins  when  food  enters  the  mouth  and  ends 
when  its  products  are  ready  for  absorption  by  the  blood 
and  lymph. 

Digestion  in  the  Mouth.  The  first  process  to  which 
the  food  is  subjected  is  mastication,  or  chewing.   In  this  proc- 


THE  ANIMAL  AND  IT8  PRODUCTS 


259 


ess  it  is  moistened  by  the  saliva.  This  is  a  liquid  secretion 
poured  out  by  special  organs  called  glands,  located  in  the 
cheeks  and  beneath  the  tongue.  It  is  a  very  watery  fluid, 
containing  not  more  than  one  per  cent  of  solids.  These 
solid  substances  are  very  important,  however.  Chief  among 
them  is  the  enzyme  called  ptyalin.  This  enzyme  changes 
starch  to  maltose  in  a  slightly  alkaline  medium.  Saliva  is 
slightly  alkaline,  due  chiefly  to  the  presence  of  bicarbonate 
and  phosphate  of  potassium.  Man  secretes  about  a  quart 
of  this  fluid  daily.  An  ox  secretes  fifty  times  as  much. 
Does  this  not  show  that  the  salivary  glands  are  very  active? 
Except  possibly  in  cud-chewing  animals,  the  food  does  not 
remain  in  the  mouth  long  enough  for  much  digestion  to 
occur  there.    After  it  has  been  mixed  with  the  saliva  it  is 

swallowed  into  the 
stomach  through  the 
oesophagus  or  ''gullet." 
There  the  action  of 
ptyaHn  continues.  How 
does  the  difference  of 
solubility  between 
starch  and  maltose 
promise  to  render  the 
work  of  ptyalin  import- 
ant in  the  later  absorp- 
tion of  the  food?  Can 
you  not  suggest  how 
chewing  favors  com- 
plete action  of  the  sali- 
va upon  the  food? 
Digestion    in    the 

Figure  71.     Stomach  of  the  horse.      The  probes    c+rw.vioo^i       Tr^  +l^r^  c.+/-wrvi 
show  the  openings  of  pancreatic  and  bile  ducts    OlOmacn.     in  ine  SlOm- 
into  the  intestine.  u    xi.       r       j      •  j.    j 

ach  the  food  is  acted 
upon  by  the  gastric  juice.  This  is  a  secretion  poured 
from  the  cells  of  the  inner  lining  of  the  stomach.     It  is  a 


260  CHEMISTRY  OF  THE  FARM  AND  HOME 

watery  fluid,  like  saliva,  but  is  acid  in  reaction.  You  may- 
have  observed  this  acidity  when  some  of  the  stomach  con- 
tents has  been  returned  to  the  mouth  from  an  unsettled 
stomach.  It  is  due  to  the  presence  of  about  0.2  per  cent 
HCl  in  the  gastric  juice.  Digestion  by  saliva  continues  for 
a  time  in  the  forepart  of  the  stomach.  Gradually,  how- 
ever, the  alkalinity  of  the  saliva  is  neutralized  by  the  acid 
of  the  gastric  juice.     Then,  in  the  acid  contents  of  the 


Figure  72.  Stomach  of  a  sheep.  The  parts  of  the  sheep's  stomach 
from  right  to  left  are:  Rumen,  reticulum,  omasum  or  "many- 
plies"  and  abomasum  or  "rennet."  The  oesophagal  groove  is 
seen  just  over  the  reticulum.  „        .  „  „  ,  .  „ 

'  Copyright  1889  by  D.  Appleton  &  Co. 

stomach,  ptyalin  is  destroyed.  The  work  of  digestion  is 
taken  up  at  this  point  by  enzymes  of  the  gastric  juice. 
Rennin  and  pepsin  are  the  most  important  of  these  enzymes. 
The  former  coagulates  or  curdles  the  casein  of  milk.  The 
latter,  by  causing  cleaving  reactions  of  the  proteins  with 
water,  converts  these  relatively  insoluble  compounds  into 
simpler,  soluble  compounds,  the  proteoses  and  peptones. 
From  time  to  time,  as  the  food  is  digested,  the  ring-like 
muscle  at  the  pylorus  relaxes.  At  the  same  time  the  mus- 
cular walls  of  the  stomach  contract  and  force  the  chyme, 
or  contents  of  this  organ,  into  the  intestines. 

The  stomach  of  ruminants,  or  cud-chewing  animals,  is 
much  more  complicated  than  that  of  man  and  the  other 
non-ruminants.  It  consists  of  four  parts,  as  shown  in 
Figure  72.  These  parts,  named  in  order  from  the  oesoph- 
agus, are:    (l)  the  rumen  or  paunch,    (2)  the  reticulum  or 


THE  ANIMAL  AND  ITS  PRODUCTS  ^61 

honeycomb,  (3)  the  many-pUes,  and  (4)  the  rennet.  The 
paunch  is  a  reservoir  in  which  the  coarse  food  may  be  stored 
until  it  is  returned  to  the  mouth  for  mastication.  You 
must  have  sometimes  observed  the  gullet  movements  by 
which  the  cow  accomplishes  this  return  to  the  mouth.  The 
paunch  of  an  ox  is  surprisingly  large.  It  may  reach  a  ca- 
pacity of  over  fifty  gallons.  In  it  fermentation  of  the  food 
occurs  constantly,  due  to  the  action  of  bacteria  and  other 
organisms.  The  resulting  gases  are  generally  removed  by 
the  blood.  Sometimes,  though,  animals  gorge  the  paunch 
with  easily  fermentable  material,  such  as  green  clover  or 
fruit,  and  serious  bloating  occurs.  In  such  cases  the  pres- 
sure of  gases  must  be  reHeved  by  stabbing  or  "tapping" 
through  the  side  of  the  body  to  prevent  death. 

The  honeycomb  receives  food  from  both  the  gullet 
and  the  paunch.  It  is  a  sort  of  safety  trap  which  catches 
in  its  rough  lining  such  accidental  objects  as  stones  and 
pins.  Look  up  in  your  dictionary  the  meaning  of  the 
adjective  ' 'reticulate."  Does  it  show  any  reason  for  the 
scientific  name  "reticulum"  applied  to  the  honeycomb? 

The  many-plies,  or  third  stomach,  receives  directly 
from  the  gullet  such  food  as  is  in  a  finely-ground  condition. 
This  is  done  by  the  automatic  closing  of  the  slit  opening 
into  the  honeycomb.  An  arrangement  called  the  oesoph- 
agal  groove  is  thus  formed  which  directs  the  food  to  the  third 
stomach.  The  lining  of  this  part  of  the  stomach  is  thrown 
up  into  folds  which  have  a  grinding  action  somewhat  like 
that  of  the  gizzard  of  fowls. 

The  rennet,  or  fourth  stomach,  accomplishes  the  digestion 
by  gastric  juice.  It  is  this  part  of  the  stomach  which  is 
very  active  in  calves  in  secreting  the  enzyme  rennin  and 
is  used  for  preparing  rennet  extract  for  cheese-making. 
Here,  also,  pepsin  does  its  work  in  the  way  already  described. 

In  fowls,  as  you  know,  the  process  of  chewing  and  the 
action  of  saliva,  are  almost  totally  lacking.     The  crop  of 


262 


CHEMISTRY  OF  THE  FARM  AND  HOME 


these  animals  has  much  the  same  uses  as  the  paunch  of 
ruminant  animals.  This  is  connected  with  the  gizzard 
by  an  enlarged  portion  of  the  oesophagus  which  forms  the 
first  stomach.  The  gizzard  is  the  chief  digestive  organ. 
Very  likely  you  have  seen  its  thick,  muscular  coat  and  its 
tough,  wrinkled  lining.  It  is  very  well  suited  to  the  grinding 
of  tough  food  materials.  The  chewing  and  protein  digest- 
ing of  the  fowl  are  done  chiefly  by  this  organ. 

Digestion  in  the  Intestines.  The  intestines  consist 
of  a  long,  slender,  much-coiled  part  followed  by  a  shorter, 

wide  part.  In  the  former 
part,  or  small  intestine, 
both  digestion  and  absorp- 
tion occur.  In  the  latter 
part,  or  large  intestine,  the 
undigested  residues  of  the 
food  and  other  waste  pro- 
ducts are  assembled  and 
expelled  from  the  body. 
When  one  learns  the  total 
length  of  the  intestines  it 
is  possible  to  realize  what 
a  large  share  of  the  work 
of  digestion  they  can  per- 
form.    This  length  ranges 

Figure  73.     Some    of   the    most    important     from   about   80   fect  in  the 
internal  organs  of  the  hog.  .  «.  .  , 

pig  to  190  feet  m  the  ox. 
Movement  of  material  along  these  organs  is  caused  by 
muscular  contractions  which  traverse  them  like  waves  from, 
the  stomach  toward  the  anus,  or  excretory  orifice. 

When  the  food  mass  enters  the  intestines  from  the 
stomach  it  has  an  acid  reaction.  This  is  soon  neutralized, 
however,  by  alkalies  and  then  the  digestive  action  of  the 
gastric  juice  ceases.  The  alkalies  are  contributed  by  the 
bile  and  the  pancreatic  juice.     These  are  secretions  from 


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'  iN-^Ci  r/ive- 

'    '   iL   '-^^'^'^ 

BihtiliEK  0 

fc^^ 

THE  ANIMAL  AND  ITS  PRODUCTS 


263 


the  liver  and  pancreas,  or  * 'sweetbread/'  respectively. 
They  are  poured  into  the  intestines  through  openings  near 
its  union  with  the  stomach.  The  pancreatic  j  uice  is  slightly 
alkaline  from  its  content  of  sodium  carbonate.  It  also  con- 
tains three  important  enzymes.  These  are  trypsin,  steap- 
sin,  and  amylopsin.  Trypsin  takes  up  in  this  alkaline  fluid 
the  work  dropped  by  pepsin,  carries  it  much  farther  and 
reduces  the  proteins  even  to  amino  acids.  Amylopsin  con- 
tinues the  work  of  ptyalin,  converting  starch  to  maltose. 

This  work  is  very  completely 
done,  as  no  starch  is  excreted 
from  the  body.  Steapsin  is  related 
to  the  lipase  of  plant  seeds.  It 
converts  fat  into  glycerine  and 
fatty  acids.  All  these  enzymes  act 
by  hydrolysis,  that  is,  by  causing 
their  respective  compounds  to 
unite  with  water  and  split  asun- 
der. The  bile  is  the  greenish 
liquid  stored  in  a  sac  attached  to 

Figure  74.     The  inner  wall  of  the  the    Hver   wMch  is  Called    the  ''gall 

small  intestine  near  the  stomach.  ,  ,      ,  , 

Near  the  center  can  be  seen  the  bladder."  It      COUtainS      alkaline 

opening    of    ducts     which    dis-  i  /•         t  .         ,        . 

charge  the  pancreatic  juice  and  SaltS  of  SOdmm   COmblUed  with   Or- 
bile. 

game  acids.  These  help  to  neu- 
tralize the  acid  of  the  chyme;  but,  especially,  they  assist 
in  the  digestion  and  absorption  of  fats. 

The  lining  of  the  small  intestines  also  secretes  enzymes. 
One  of  these,  maltase,  changes  maltose  to  glucose.  An- 
other, erepsin,  splits  digestion  products  of  proteins  complete- 
ly to  amino  acids. 

Absorption  of  Digested  Food.  All  the  various  products 
of  digestion,  dextrose,  amino  acids,  fatty  acids  and  so  on, 
are  absorbed  by  the  blood  and  lymph  through  the  physical 
and  chemical  activity  of  the  cells  of  the  mucuos  membrane 
lining  the  intestine.     Figure  74  shows,  as  you  can  verify 


264 


CHEMISTRY  OF  THE  FARM  AND  HOME 


by  observation,  that  this  lining  is  thrown  up  into  many  folds. 
This  arrangement  greatly  increases  the  absorbing  surface 
over  what  a  smooth  lining  would  present.  These  folds 
are  thickly  threaded  by  blood  capillaries  and  lymph  vessels. 
Dextrose  and  protein  digestion  products  find  their  way  into 
the  blood  and  are  carried  to  the  liver  by  a  large  vein.  This 
organ  converts  any  extra  dextrose  to  a  polysaccharide  called 
glycogen.  It  also  stores  some  of  the  excess  of  amino  acids. 
When  the  food  supply  is  low  the  glycogen  is  changed  back 
to  dextrose  and  the  stored  compounds  are  doled  out  to  the 

blood.  In  this  way  it 
serves  as  a  regulator  of 
the  composition  of  the 
blood.  The  fatty  acids 
and  glycerine  are  absorbed 
by  the  lymph  converted 
to  fats  and  passed  into  the 
blood  in  the  neck.  Un- 
digested portions  of  the 
food  pass  from  the  large 
intestines  as  feces,  or 
dung.  With  it  are  includ- 
ed the  waste  of  fatty  se- 
cretions from  the  bile  and 
Figure  75.  protciu     material     added 

from  dead  tissue  swept  from  the  walls  of  the  intestine  and 
from  bacteria  which  developed  in  this  organ. 

Circulation  of  the  blood  carries  the  absorbed  food  com- 
pounds to  the  remotest  tissues  of  the  body.  From  the 
veins,  as  you  learned  in  physiology,  the  blood  is  collected 
at  the  right  side  of  the  heart  and  forced  to  the  lungs.  Here 
the  purple  fluid  of  the  veins  is  changed  to  the  scarlet  of  the 
arteries  and  returned  to  the  left  side  of  the  heart.  This 
change  of  color  is  due  to  the  absorption  of  oxygen  from  the 
air  in  the  lungs.     The  arterial  blood  is  pumped  to  all  the 


CAflLLAKICS    I 


DIAGRAM   or  BLOOD   CIRCULATION 


THE  ANIMAL  AND  ITS  PRODUCTS 


266 


tissues  of  the  body.  The  individual  cells  of  the  tissues 
remove  the  oxygen  and  food  compounds  for  work  and  build- 
ing processes.  They  excrete  their  waste  products  into  the 
purple  blood  which  collects  in  the  veins  to  begin  the  round 
of  the  body  again. 

Respiration  is  more  than  the  mere  physical  act  of  breath- 
ing.    It  does  not  occur,  as  commonly  thought,  in  the  lungs. 

Breathing  is  mere- 
ly one  step  in  the 
process.  The  air 
which  one  exhales 
from  the  lungs  con- 
tains only  three 
fourths  as  much 
oxygen,  but  one 
hundred  and  fifty 
times  as  much  car- 
bon dioxide  as  the 
fresh  air  breathed 
in.  This  difference 
is  due  to  the  re- 
lease of  carbon  di- 


Figure  76. 


The  lunga,  showing  their  close  relation  to 
the  heart. 
Copyright  1889  by  D.  Appleton  &  Co, 

oxide  from  bicarbonate  of  sodium  in  the  blood  and  to  the 
taking  up  of  oxygen  to  form  the  scarlet  oxyhaemo-globin. 
Figure  76  shows  how  the  much-divided  tissue  of  the  lungs 
thickly  traversed  by  blood  vessels  favors  a  rapid  exchange 
of  gases  between  the  air  and  blood.  True  respiration  occurs 
only  when  this  increased  oxygen  of  the  blood  has  reached 
the  cells  in  need  of  it  by  the  circulation  already  described. 
Assimilation  includes  the  use  of  food  compounds  absorbed 
from  the  intestine  and  oxygen  absorbed  in  the  lungs.  It 
occurs,  as  you  can  see,  only  when  the  bright,  arterial  blood 
reaches  the  particular  cells  in  need.  The  chemical  changes 
of  growth  and  work  are  included  in  it.  Certain  food  com- 
pounds, especially  dextrose,  are  oxidized,  or  burned,  to  do 


266  CHEMISTRY  OF  THE  FARM  AND  HOME 

work.  This  process  is  very  rapid  in  the  muscle  cells  when 
the  body  is  doing  outside  work.  Other  compounds,  especial- 
ly proteins,  are  modified  in  various  ways  to  build  new  cells 
and  tissues. 

Excretion  is  the  process  of  getting  rid  of  the  wastes  of 
the  body.  Not  only  must  undigested  food  be  expelled, 
but  also  the  waste  products  from  oxidation  and  growth 
in  the  various  cells  must  be  removed.  What,  for  example, 
are  the  products  of  oxidation  of  dextrose  when  burned? 
Do  you  see  in  your  answer  an  explanation  for  the  large 
amount  of  carbon  dioxide  in  venous  blood? 

Chief  among  the  waste  products  from  cells  of  the  body, 
besides  carbon  dioxide  and  water,  are  salts  and  soluble 
nitrogen  compounds  resulting  from  proteins.  The  most 
abundant  of  these  nitrogen  compounds  is  urea,  a  close 
relative  of  ammonia. 

The  excretion  of  carbon  dioxide  occurs,  as  we  have 
seen,  from  the  lungs  by  way  of  the  blood.  Some  water 
is  also  given  off  from  the  lungs,  as  you  can  prove  for  your- 
self by  breathing  against  a  windowpane  in  cold  weather. 
As  the  breath  is  cooled  it  can  no  longer  hold  all  the  moisture 
present  as  it  leaves  the  lungs.  Hence  water  condenses  in 
droplets  upon  the  pane. 

The  skin  also  excretes  water.  Have  you  not  observed 
in  the  case  of  your  own  body  that  vigorous  exercise  and  rapid 
perspiration  or  ' 'sweating' '  go  hand-in-hand?  This  is  a 
means  by  which  the  excess  of  water  produced  by  oxidation 
in  the  cells  of  the  working  muscles  is  removed  from  the 
body.  Nature  has  also  wonderfully  provided  that  the  heat 
required  to  evaporate  this  perspiration  shall  cool  the  body. 
To  this  same  end  the  dog  instinctively  pants  with  out- 
stretched tongue  to  increase  the  evaporating  surface  of  his 
body.  That  perspiration  contains  dissolved  salts  is  well 
shown  by  its  taste.  What  salt  have  you  detected  in  it? 
It  also  contains  various  waste  organic  compounds. 


THE  ANIMAL  AND  ITS  PRODUCTS  267 

The  kidneys  are  the  fourth  important  organ  of  excretion. 
As  you  see  by  Figure  77  the  same  principle  is  made  use  of 
in  their  structure  as  in  the  case  of  the  lungs.  Minute 
blood  vessels  thickly  thread  a  mass  of  spongy  tissue.  The 
pores  of  this  tissue  increase  in  size  toward  the  center,  from 
which  the  urine  is  finally  drained  away 
for  storage  in  the  bladder.  By  their  re- 
markable powers  the  cells  of  this  organ 
receive  on  one  side  the  waste-laden 
blood  and  excrete  on  the  other  side 
their  special,  selected  product,  the 
urine.  The  blood  is  then  passed  on, 
purified  and  ready  to  repeat  its  work 
of  carrying  both  food  and  waste  mat- 
ter. The  wastes  removed  from  the 
blood  by  the  kidneys  are  chiefly  water, 
salts,  and  nitrogen  compounds.  Or- 
dinarily they  remove  about  as  much 

Figure  77.     Section  through  n      .  i  .  i 

a  kidney  and  the  channel   Watcr    aS     all     the    Othcr    OrganS    COm- 
leading  to  the  bladder.  i  •        i         x  •     i  i  i  i 

bmed.  In  wmter,  however,  when  loss 
of  water  from  the  skin  is  small,  the  urine  increases  in  amount. 
The  kidneys,  like  the  liver,  are  hard-working  servants  of 
the  body. 

Measure  of  the  Digestibility  of  Feeding  Stuffs.  The 
digestibility  of  a  feeding  stuff  is  measured  by  the  difference 
between  its  dry  matter  and  the  dry  matter  of  the  dung 
produced  from  it.  Generally,  the  digestibiUty  of  the 
protein  and  other  constituents  of  the  food  are  measured 
in  this  same  way.  Suppose,  for  example,  100  pounds  of 
feeding  stuff,  containing  10  per  cent  of  protein,  produces 
180  pounds  of  manure  containing  3  per  cent  of  protein. 
Then  10  pounds  of  protein  are  fed  and  5.4  pounds  are  ex- 
creted. The  digestibility  of  the  protein  of  this  feed  is, 
therefore,  46  per  cent.  From  what  we  learned  about  bac- 
teria and  other  foreign  matter  excreted  with  the  undigested 


268 


CHEMISTRY  OF  THE  FARM  AND  HOME 


food  you  can  see  that  this  method  does  not  exactly  measure 
digestibility.  Yet  it  has  been  a  valuable  means  for  com- 
paring the  values  of  different  feeding  stuffs.  At  one  time 
these  measurements  were  made  by  catching  the  feces  in 
a  bag  harnessed  to  the  animal.  The  modern  method  is 
to  place  the  animal  in  a  cage  of  the  sort  shown  in  Figure 
78.     In  such  an  apparatus  both  feces  and  urine  can  be 

accurately  collected.  By 
analyzing  the  urine  chem- 
ists are  learning  a  great 
deal  about  the  way  in 
which  animals  use  the 
digested  portion  of  the 
food. 

The  products  of  farm 
animals  vary  a  great  deal 
in  nature.    That  obtained 

Figure  78.     Cage    used   in  digestion    experi-  »  .  i         i  •  i 

ments.     The  larger  part   has  a  bottom  of  irom    the     horSe    IS     WOrK. 

wire  screening  to  catch  feces  and  a  sloping,  ^  ,  ,         .  - 

tinned  bottom  beneath  that  to  collect  the  It    may    take    the   lOrm    01 
urine.  The  smaller  part  is  the  feeding  cage.       . , ,  i       <»  . 

either  speed  of  movement 
or  pull,  or  "draft."  In  animals  which  serve  for  food,  such  as 
the  pig,  the  product  is  meat  composed  chiefly  of  protein  and 
fat  compounds.  These  animals  do  work  by  their  growth  to 
provide  a  product  for  the  use  of  man.  It  is  j  ust  as  truly  work 
done  by  the  cells  of  the  body  as  is  muscular  exertion.  The 
pig  is  by  far  the  most  eflficient  producer  of  this  kind.  When 
lean,  his  carcass  dresses  about  three  fourths  of  his  live  weight. 
The  sheep  and  ox  dress  to  only  about  one  half  of  their  live 
weight.  This  difference  is  due  to  the  smallness  of  bones 
in  the  pig  as  compared  with  the  other  animals.  Fattening 
mature  animals  produce  very  efficiently,  as  practically 
all  the  tissue  they  build  forms  valuable  food  for  man.  It  is 
subject  to  little  waste. 

The  sheep  produces  wool  as  well  as  meat.     Pure  wool 
is  a  protein  compound,  but  the  raw,  unwashed  material  is 


THE  ANIMAL  AND  ITS  PRODUCTS  269 

coated  with  a  greasy  substance  called  ''suint."  This  sub- 
stance is  a  mixture  of  fats,  soaps,  salts,  and  other  compounds 
left  on  the  wool  by  evaporating  perspiration.  On  account 
of  the  fatty  nature  of  suint  the  raw  wool  is  quite  readily 
cleansed  by  washing  with  soap. 

The  cow  produces  milk  in  addition  to  meat.  As  we  shall 
see  later,  this  is  a  very  special  product  of  complex  nature. 
It  contains  proteins,  fats,  sugar  and  characteristic  salts. 
Tri-calcium  phosphate  is  an  important  constituent  of  milk. 

Fowls  produce  both  meat  and  eggs.  The  latter  contain 
chiefly  protein  compounds  with  smaller  amounts  of  fats  and 
related  compounds.  Since  the  egg  performs  the  duty  of 
reproduction,  we  find,  as  was  learned  of  reproductive  cells, 
that  the  phosphorus-containing  nucleo-proteins  are  abundant 
in  it.     The  egg  shell  is  formed  from  calcium  carbonate. 

The  relative  efficiency  of  various  animals  to  produce 
human  foods  from  a  given  amount  of  feeding  stuffs  ought 
to  be  of  great  interest.  It  is  given  in  the  following  figures. 
They  represent  the  pounds  of  food  produced  from  100  pounds 
of  digestible  organic  matter  in  feeding  stuffs. 

Cow,  (in  milk)  18.0;  pig,  15.6;  calf,  8.1;  fowl,  (in  eggs) 
5.1;  fowl,  (in  meat)  4.2;  steer,  2.5. 

Notice  what  animal  heads  the  list.  She  is  followed 
closely  by  the  pig,  who  far  excels  the  other  meat-producing 
animals.  Do  these  relative  producing  values  give  you  any 
insight  to  reasons  why  dairying  is  a  profitable  kind  of  farm- 
ing? Do  they  suggest  why  the  handUng  of  pigs  helps  to 
make  farming  successful? 

By-products  Obtained  from  Animals.  Several  important 
by-products  are  obtained  from  animals.  The  preparation 
of  several  of  them  for  use  supports  important  industries. 
Leather  is  a  by-product  of  the  great  beef-packing  industry. 
Its  preparation  for  use  embraces  the  tanning  industry. 

Tanning  consists  in  removing  the  hair  and  preserving 
the  skin  in  a  pHable  condition.     The  hair  is  softened  by  the 


270 


CHEMISTRY  OF  THE  FARM  AND  HOME 


THE  ANIMAL  AND  ITS  PRODUCTS  271 

action  of  steam  or  of  some  slightly  alkaline  compound  such 
as  calcium  sulphide,  and  scraped  from  the  skin.  We  shall 
learn  more  about  this  loosening  effect  of  the  calcium  sulphide 
when  we  study  insecticides.  After  the  hair  is  removed  the 
skin  is  soaked  in  a  solution  of  some  preserving  substance. 
Tannin,  chromic  oxide,  and  alum  are  commonly  used. 
Tannin  is  extracted  from  barks,  commonly  from  oak  bark. 


Fi  gure  80.  Making  soap.  Grease  and  alkali  are  boiled  by  steana  in  huge  vats 
three  or  four  stories  deep.  Soap  is  an  important  by-product  of  the  meat- 
packing industry. — Courtesy  of  Swift  &  Co. 

for  this  purpose.  It  is  a  plant  product  closely  related  in  its 
chemical  composition  to  the  coal  tar  compounds.  By  com- 
bining with  the  proteins  it  forms  less  soluble  compounds 
which  resist  decay  better  than  the  natural  protein  matter 
of  the  skin.  Chromic  oxide  acts  by  partly  oxidizing  the 
proteins  of  the  skin. 

Tankage  and  dried  blood  are  prepared  from  the  wastes 
of  the  packing  industry.  The  carcasses  of  condemned  and 
aged  animals  are  also  made  into  these  products.  By  quickly 
drying  the  materials  in  large  steam-heated  pans  they  are 


272      CHEMISTRY  OF  THE  FARM  AND  HOME 

rid  of  bacteria  and  guarded  from  decay.  They  are  also 
more  cheaply  handled  after  their  water  has  been  removed 
by  drying.  These  products  are  valued  as  concentrated 
foods  supplying  protein  and  ash  for  pigs  and  fowls.  Their 
greatest  use,  however,  is  as  sources  of  nitrogen  and  phos- 
phorus for  fertilizers.  Gelatine,  mentioned  before,  is  a 
product  obtained  by  steaming  cartilage  and  tendon  tissues. 
Glue  is  made  in  this  way  from  hoof  and  horn.  Horn  is 
also  cut  into  buttons  and  many  other  useful  articles. 

SUMMARY 

The  body  of  the  living  animal  is  a  wonderfully  arranged,  automatic 
factory.  Materials  by  which  this  factory  keeps  in  repair  and  fuel 
from  which  it  obtains  power  are  provided  by  plants  in  the  form  of  food. 

In  structure  the  body  consists  of  the  skeleton,  vital  organs,  muscles 
and  skin.  The  actions  of  these  various  parts  are  brought  into  harmony 
by  the  nerves.  Their  chemical  reactions  are  inter-related  through 
the  blood   and   its   circulation. 

In  chemical  composition  the  bony  skeleton  is  chiefly  tri-calcium 
phosphate  and  the  other  organs  are  mixtures  of  protein  compounds. 
Hair,  horn  and  hoof  are  modified  forms  of  the  skin  proteins. 

Water  forms  the  greater  part  of  the  weight  of  animals.  The 
remainder  of  the  body  is  chiefly  proteins  in  lean  animals  and  fats  in 
fat  animals.  Oxygen  forms  two  thirds  of  the  body  weight,  while  several 
other  elements  occur  in  amounts  from  a  trace  to  a  few  per  cent.  Some 
of  the  elements  present  in  small  amount,  such  as  chlorine,  are  as  essen- 
tial to  life  in  the  long  run  as  oxygen.  Those  elements  important  in 
the  fertihty  of  the  soil  are  present  in  smaller  amounts  in  the  pig  than 
in  other  animals,  for  the  reason,  previously  stated  that  it  has  a  low 
proportion  of  bone  and  a  high  proportion  of  fat  in  its  body. 

Animal  nutrition  includes  the  physical  and  chemical  processes 
which  repair  and  increase  the  tissues  of  the  body.  Its  four  chief 
steps  are  digestion,  absorption,  assimilation  and  excretion.  Diges- 
tion is  performed  by  enzymes  contained  in  fluids  secreted  by  special 
organs  called  "glands."  It  occurs  not  only  in  the  mouth  and  stomach, 
but  also  in  the  intestine.  Digestion  reduces  the  compounds  of  the  food 
to  soluble  products.  Absorption  is  the  process  in  which  these  products 
are  taken  up  through  the  intestine  wall  into  the  circulating  blood  and 
carried  to  the  tissues.  It  includes  the  taking  up  of  oxygen  by  the  blood 
in  the  lungs.     Water  is  of  great  importance  in  the  chemical  reactions 


THE  ANIMAL  AND  ITS  PRODUCTS  273 

of  digestion  and  the  physical  processes  of  absorption.  Assimilation 
includes  the  processes  in  which  oxygen  and  products  of  digestion  are 
removed  from  the  blood  and  used  by  the  various  cells  in  need.  The 
assimilation  of  oxygen  is  separately  known  as  "respiration."  Ex- 
cretion is  the  process  of  removal  of  waste  products  from  chemical 
reactions  in  the  various  cells  of  the  body.  It  covers  the  absorption  of 
these  compounds  by  the  blood  and  their  final  expulsion  from  the  lungs, 
skin  and  kidneys.  Undigested  feeding  stuff  and  some  waste  materials 
are  excreted  by  the  intestine.  The  difference  between  the  composition 
of  the  food  and  of  the  intestinal  excreta  produced  from  it  is  used  as  a 
measure  of  the  digestibiUty  of  feeding  stuffs. 

The  products  of  animals  made  use  of  by  man  are  work  and  food. 
In  power  to  produce  human  food  from  a  given  amount  of  their  feeding 
stuffs  the  milch  cow  and  the  pig  far  excel  other  farm  animals.  Dairy- 
ing and  the  handhng  of  swine  have  come,  therefore,  to  be  the  most 
generally  profitable  kinds  of  farming.  By-products  from  the  great 
meat-packing  industries  provide  in  themselves  industries  of  considerable 
importance.     They  include  leather,  tankage,  glue  and  horn  articles. 

QUESTIONS 

1.  What  is  the  composition  of  bones? 

2.  What  is  the  composition  of  the  muscles  and  vital  organs? 

3.  What  is  the  composition  of  haemoglobin?     Its  functions? 

4.  What  are  the  chief  compounds  of  nerve  tissue? 

5.  How  much  water  is  there  in  the  body  of  a  lean  ox? 

6.  What  chemical  element  is  most  abundant  in  the  human  body? 

7.  What  element  unessential  to  plants  is  essential  to  animals? 

8.  What  is  the  action  of  saliva  on  foods? 

9.  What  is  the  action  of  gastric  juice  upon  the  foods? 

10.  What  three  important  enzymes   are  in  pancreatic  juice? 

11.  What  work  does  each  perform? 

12.  What  digestive  process  is  assisted  by  the  bile? 

13.  What  effects  does  the  liver  exert  on  the  composition  of  the 
blood? 

14.  What  compounds  of  the  food  are  absorbed  by  the  lymph 
after  digestion? 

15.  What  important  chemical  change  occurs  to  the  blood  in  the 
lungs? 

16.  Where  does  assimilation  of  the  digested  food  occur? 

17.  What  is  the  source  of  the  carbon  dioxide  excreted  from  the 
lungs?     Of  the  water  excreted  in  perspiration? 

18.  What  wastes  are  excreted  by  the  kidneys? 

19.  How  is  the  digestibility  of  feeding  stuffs  measured? 

20.  What  are  the  chief  compounds  of  milk?     Of  eggs? 

21.  What  two  animals  excel  as  producers  of  human  food? 

22.  How  are  hides  tanned? 

23.  How  are  gelatine  and  glue  made? 

18— 


CHAPTER  XI 
THE  FEEDING  OF  ANIMALS 

Scientific  Foundation  of  Feeding.  On  the  title  page  of 
his  well-known  book  ''Feeds  and  Feeding,"  Professor  Henry- 
has  placed  the  following  German  adage:  ''The  eye  of  the 
master  fattens  his  cattle."  It  is,  indeed,  true  that  a  watch- 
ful eye  is  necessary  to  the  farmer  who  would  secure  the  best 
possible  returns  from  the  feeding  of  animals.  Perhaps  you 
know  such  a  master-feeder  in  your  own  neighborhood.  He 
must  be  a  man  quick  to  detect  the  response  of  each  of  his 
animals  to  different  kinds  of  treatment.  In  the  past,  the 
observations  of  such  keen  stockmen  have  created  quite  a 
compendium  of  opinions  on  the  subject  of  feeding.  These 
opinions  have  the  attractive  quality  of  being  expressed  in 
simple  and  very  practical  language.  Much  faith  has  been 
placed  in  them  by  the  average  farmer.  We  must  remember, 
however,  that  at  best  they  express  but  roughly  some  of  the 
scientific  principles  which  underlie  the  nutrition  of  the 
animal.  Like  other  arts,  the  feeding  of  animals  has  under- 
gone sure  and  rapid  development  only  when  guided  by 
scientific  principles.  It  is  clearly  recognized  by  scientists 
that  uniform  and  sure  results  can  be  obtained  by  the  feeder 
in  but  one  way.  That  way  is  pointed  out  by  principles 
carefully  determined  by  studies  in  chemistry  and  physiology. 
We,  therefore,  ought  to  study,  in  as  simple  terms  as  possible, 
the  scientific  principles  which  regulate  the  feeding  of  animals. 

Nature  and  Composition  of  Feeding  Stuffs.  In  our 
study  of  the  animal  we  learned  that  its  body  resembles  a 
factory  for  which  food  serves  as  repair  material  and  fuel. 
Let  us  now  inquire  into  the  nature  and  composition  of  feed- 
ing stuffs.     These  food  substances  consist  of  a  great  number 

274 


THE  Feeding  of  animals  275 

of  compounds  which  the  chemist  divides  by  analysis  into 
six  groups.  These  are:  water,  protein,  fat,  fiber,  nitrogen- 
free  extract,  and  ash.  The  amount  of  water  varies  greatly 
between  fresh  and  cured  feeding  stuffs.  Turnips  and  other 
roots  contain  about  90  per  cent,  green  fodders  contain  about 
80  per  cent,  and  cured  grains  and  hays,  in  the  condition 
called  ''air  dried, '*  contain  only  about  10  to  15  per  cent. 
The  term  ''crude  protein"  includes  all  the  nitrogen  com- 
pounds of  the  feeding  stuff.  For  our  purposes  it  may  be 
regarded  as  consisting  of  protein  compounds.  Its  amount 
varies  widely.  Only  one  or  two  per  cent  is  present  in  fresh 
root  crops  and  green  hays,  but  in  cured  clover  and  legume 
hays  and  in  grains  10  to  14  per  cent  is  present.  In  some 
special  grain  products,  such  as  cottonseed  meal,  protein 
forms  almost  one  half  of  the  material.  The  amount  of  fat 
varies  from  a  few  tenths  of  one  per  cent  in  root  crops  and 
green  hays  to  about  5  per  cent  in  grains.  It  is  commonly 
called  "ether  extract."  This  is  a  more  correct  name  than 
fat,  because  chlorophyll,  which  is  not  a  fat,  forms  a  large 
part  of  the  material  extracted  from  hay  by  ether.  Fiber  is 
a  mixture  of  cellulose  compounds.  The  impure  product  sep- 
arated by  the  chemist  is  called  ''crude  fiber."  Its  amount 
varies  from  2  per  cent  in  some  grains  to  30  per  cent  in 
some  hays.  Nitrogen-free  extract  includes  chiefly  starch 
and  other  carbohydrates  made  soluble  by  boiling  the  feeding 
stuff  with  weak  acid  and  weak  alkali  successively.  Do  you 
not  see  that  it  is,  indeed,  an  extract  material  free  from 
nitrogen?  Its  amount  varies  from  about  40  per  cent  in 
hays  to  70  per  cent  or  more  in  grains  and  mill  products. 
The  reason  for  separating  fiber  from  the  other  carbohydrates 
in  analysis  will  become  clear  when  we  learn  how  slight  is 
its  service  to  the  animal.  The  ash  includes  those  elements 
recombined  and  left  behind  by  burning,  as  already  described 
in  the  chapter  upon  the  plant.  Its  amount  ranges  from  1 
per  cent  in  green  fodders  and  some  grains  to  nearly  6  per 


276  CHEMISTRY  OF  THE  FARM  AND  HOME 

cent  in  wheat  bran  and  other  mill  products.  Of  these  several 
groups  of  compounds  only  four  will  need  much  of  our  atten- 
tion. These  are  the  protein,  fat,  nitrogen-free  extract,  and 
ash.  It  will  be  helpful  to  think  of  the  nitrogen-free  extract 
simply  as  digestible  carbohydrates.  Now  we  can  regard  the 
uses  of  these  compounds  in  the  feeding  of  the  animal. 

Building  and  Fuel  Values  of  Feeding  Stuffs.  On  the 
one  hand,  proteins  are  the  important  building  and  repairing 
materials  of  the  food.  On  the  other  hand,  fats  and  carbo- 
hydrates serve  as  the  sources  of  heat  and  power.  We  have 
seen  that  each  cell  of  the  animal  body  is  constructed  chiefly 
from  proteins.  Growth  makes  necessary  an  increase  of 
this  protein  material.  The  destructive  effects  of  work  makes 
necessary  its  repair.  We  should  realize  that  the  protein 
compounds  of  feeding  stuffs  supply  these  needs.  No  other 
compounds  of  the  food  can  replace  proteins  in  this  work; 
for  no  other  compounds  contain  the  necessary  bricks  from 
which  to  build  proteins  of  the  body. 

The  bomb  calorimeter  is  an  instrument  by  which  one 
can  measure  the  heating  power  of  feeding  stuffs.  The  dif- 
ferent compounds  and  elements  of  feeding  stuffs  can  also 
be  compared  by  it.  One  measures  their  fuel  value  by  burn- 
ing them  completely  in  a  strong  steel  chamber  or  *'bomb" 
with  a  liberal  supply  of  oxygen.  Why  will  not  common  air 
do?  The  heat  produced  warms  the  bomb  and,  as  you  see 
by  Figure  81,  is  transmitted  to  a  definite  weight  of  water 
surrounding  it.  It  is  necessary  to  protect  the  water  from 
loss  of  heat  to  the  air.  The  question  now  arises:  How 
shall  the  amount  of  heat  be  expressed?  It  is  expressed  in 
units  called  Calories.  You  will  find  it  interesting  to  con- 
sult a  large  dictionary  and  learn  the  origin  of  this  word.  It 
is  the  quantity  of  heat  required  to  raise  one  kilogram  of 
water  from  0  to  1  degree  on  the  Centigrade  scale.  A  degree 
Centigrade  is  1 .8  times  as  great  as  a.  degree  Fahrenheit  and 
the  zero  of  this  scale  is  equal  to  32°  Fahrenheit.     There  are 


THE  FEEDING  OF  ANIMAL8 


277 


2.2  pounds  in  a  kilogram.     With  these  values  you  can,  if 

you  choose,  compute  the  value  of  a  calorie  in  pounds  of 

water  and  degrees  Fahrenheit. 

The  fuel  values  in  calories  per  gram  of  some  important 

elements   and  compounds    of  feeding  stuffs   are:     Carbon 

(charcoal)  8.00,  hydrogen, 
34.40,  protein  (wheat  gluten) 
6.00,  carbohydrate  (sucrose) 
4.00,fat(oliveoil)9.50.  These 
fuel  values  are  also  spoken 
of  as  ''energy  values,"  be- 
cause, like  the  heat  generated 
by  fuel  under  the  boiler  of  a 
steam  engine,  they  represent 
power  to  do  work,  when  set 
free  by  oxidation  in  the  ani- 
mal body.  From  the  pre- 
ceding values  we  see  that 
hydrogen  is  far  superior  to 
the  other  elements  as  fuel. 
This  fact  is  made  use  of  in 
a  very  practical  way  in  the 
oxy-hydrogen    blowpipe,    an 

Figure  81.    The  bomb  calorimeter.   Feed-  instrument      which      dcVelopS 

ing  stuffs  are  compressed  into  pellets  ,         j  v       ji                  v        j  • 

which  are  ignited  by  electricity  in    the  great  heat  by  the  COmbUStlOH 

small,  suspended  cup  and  burned  in  an  .            ,                     «•   i        i 

excess  of  oxygen.— Courtesy   of  Eimer  01   a  Stream   01   hydrOgCn  gaS 

in  oxygen.  Note  the  differ- 
ence of  the  fuel  value  between  carbon  and  carbohydrate. 
Does  it  suggest  why  the  blacksmith  chooses  charcoal  in  pref- 
erence to  coal  and  wood  for  his  forge?  Kerosene  and  other 
petroleum  oils  owe  their  heating  properties  to  the  mixtures  of 
hydrocarbons  which  they  contain.  These  compounds,  con- 
taining only  carbon  and  hydrogen,  produce  more  heat  than 
an  equal  weight  of  the  common  organic  compounds  of  feed- 
ing stuffs.  The  lower  value  of  the  latter  compounds  is  due  to 


27$ 


CHEMISTRY  OP  THE  FARM  AND  HOMP 


the  presence  of  oxygen  in  them.  They  are  already  partly  satis- 
fied by  oxygen.  Our  values  show  that  proteins,  for  an  equal 
weight  of  substance,  produce  about  1.5  times  as  much  heat 
as  carbohydrates.  Fats  are  much  more  efficient  and  pro- 
duce 2.4  times  as  much  heat  as  the  carbohydrates.  These 
differences  are  due  to  differences  in  the  amounts  of  carbon, 
hydrogen  and  oxygen  contained  in  these  compounds.  Ex- 
amine the  following  figures  and  compare  the  percentages 
of  carbon  with  the  fuel  value  of  each  compound.  Do  the 
same  for  hydrogen.     Do  the  same  for  oxygen. 


Table  IX.     The  Relation  of  Composition  to  Fuel  Value  of  the 
Compounds  of  Feeding  Stufifs. 

Per  Cent  of 

In  the 

Carbohydrate 

Dextrose 

In  the  Protein 

Zein,  of  corn 

grain 

In  the  Fat 
Olein,  of 
olive  oil 

Carbon 

40.0 
6.7 

53.3 
0.0 

100.0 

55.2 
7.3 

20.8 
16.7 

100.0 

76.6 

Hydrogen 

12.1 

Oxygen 

11.3 

Nitrogen  and  sulphur .... 
Total        ... 

0.0 
100  0 

Do  you  not  see  that  fat  owes  its  high  fuel  value  to  a 
high  ratio  of  carbon  and  hydrogen  to  oxygen?  Carbohy- 
drates have  the  lowest  fuel  value  because  already  most 
satisfied  by  oxygen.  We  can  see,  then,  that  different  pro- 
portions of  these  compounds  in  feeding  stuffs  must  produce 
different  fuel  values  for  materials  so  widely  different  in 
composition  as  timothy  hay  and  gluten  feed.  The  amounts 
of  heat  developed  by  such  portions  of  feeding  stuffs  as  are 
handled  in  making  rations  are  too  great  for  convenient 
expression  in  calories.  Professor  Armsby,  of  the  Pennsyl- 
vania Experiment  Station,  has,  therefore,  used  the  newer 
value  of  therm.  A  therm  is  one  thousand  times  as  large  as 
a  calorie.  The  fuel  values  of  100  pounds  of  some  common 
feeding  stuffs  are  as  follows:  Cornmeal,  171  therms; 
timothy  hay,  175  therms;  linseed  meal,  197  therms. 


THE  FEEDING  OF  ANIMALS  279 

We  must  remember  that  these  fuel  values  measured  by 
the  bomb  calorimeter  are  quite  different  from  the  final  fuel' 
values  of  the  feeding  stuffs  to  the  animal.  In  the  bomb 
calorimeter,  you  will  recall,  the  feeding  stuff  is  completely 
oxidized.  Is  this  true  in  the  animal  body?  Suppose  we 
were  to  dry  the  feces.  Would  they  not  burn  and  give 
heat?  The  urine  also  can  be  evaporated.  Compounds 
left  there  by  incomplete  oxidation  in  the  animal  can  then 
be  burned  in  the  calorimeter.  So  there  are  two  ways  in 
which  unused  fuel  material  escapes  the  animal:  (1)  un- 
digested fuel  compounds,  like  cellulose,  which  pass  out 
with  the  feces;  and  (2)  waste  products  from  digestion  which 
have  fuel  value,  such  as  organic  compounds  of  the  urine. 

Value  of  Indigestible  Roughage.  The  undigestible  cellu- 
lose of  feeding  stuffs  resembles  in  a  way  the  waste  clinkers 
found  in  coal  ash.  Yet  it  is  not  entirely  useless.  It  keeps 
the  material  in  the  intestines  loose.  It  also  has  an  irritating 
effect  which  causes  beneficial  movements  of  these  organs. 
Perhaps  you  have  noticed  that  farmers  avoid  using  alone 
such  feeding  stuffs  as  cottonseed  meaL  which  are  known 
as  ''concentrates"  on  account  of  their  richness  in  food  com- 
pounds. They  realize  that  a  certain  amount  of  ''roughage," 
which  includes  fibrous  feeding  stuffs,  such  as  hay,  prevents 
constipation.  On  the  other  hand,  there  is  danger  of  feed- 
ing too  much  fiber  in  the  ration,  because,  in  addition  to 
its  own  indigestibility,  it  reduces  the  digestible  amounts  of 
other  food  compounds  by  protecting  them  from  the  diges- 
tive fluids  of  the  animal.  We  can  think  of  the  cell  walls 
of  tissues  in  the  feeding  stuff  as  protecting  the  contents  of 
uncrushed  cells  in  this  way.  The  compounds  of  the  second 
class  in  which  fuel  value  leaves  the  body  are  chiefly  urea 
and  other  nitrogen  compounds  of  the  urine.  These  organic 
compounds,  as  you  will  recall,  are  waste  products  from  the 
chemical  changes  which  proteins  undergo  in  the  body. 
Since  they  are  not  completely  oxidized,  they  represent  a 


280  CHEMISTRY  OF  THE  FARM  AND  HOME 

loss  of  part  of  the  fuel  value  of  the  feeding  stuff.  To 
the  fuel  value  of  these  compounds  must  be  added  that  of 
gases  produced  by  fermentation  in  the  intestines.  The  chief 
of  these  is  methane  or  marsh  gas,  a  hydrocarbon  which 
gives  considerable  heat  when  burned.  It  is  a  waste 
product  of  digestion  and  contains  unused  fuel  value. 

Productive  Value  of  Feeding  Stuffs.  From  these  state- 
ments you  can  see  that  there  are  several  causes  which  make 
the  use  of  the  fuel  value  of  feeding  stuffs  incomplete  to  the 
animal.  In  feeding  science  the  fuel  value  of  these  waste 
products  of  digestion  is  subtracted  from  the  fuel  value  of 
the  ration  to  give  what  is  called  "the  available  energy." 
Our  study  of  fuel  value  does  not  end  here.  The  farmer 
naturally  wants  to  know  most  how  much  working  or  pro- 
ducing fuel  value  there  is  in  his  feeding  stuffs.  He  wants  the 
matter  boiled  down  to  the  merchant's  term  of  ''net  profit." 
Putting  his  problem  in  terms  of  the  steam  engine,  he  wants 
to  know  how  much  power  to  expect  after  his  fuel  material 
has  burned  and  heated  the  boiler.  One  more  item  must 
be  subtracted  from  the  total  fuel  value  of  the  feeding  stuff 
to  obtain  this  final  effective  part,  called  the  ''productive 
fuel  value."  This  last  item  is  the  loss  of  fuel  value  or  energy 
due  to  the  muscular  work  required  of  the  jaws  and  intestines. 
It  ought  to  be  readily  clear  that  much  more  work  is  re- 
quired for  chewing  a  pound  of  fibrous  timothy  hay  than 
for  the  same  amount  of  non-fibrous  cornmeal.  The  follow- 
ing statement  will  show  how  great  this  difference  is.  One 
hundred  pounds  each  of  these  two  feeding  stuffs  contain 
fuel  value  to  the  amount  of  171  and  179  therms.  Dr. 
Zuntz,  of  Germany,  measured  the  extra  amounts  of  oxygen 
required  by  a  horse  when  chewing  these  two  kinds  of  feed. 
He  found  that  twelve  times  as  much  fuel  value  was  required 
to  chew  a  hundred  pounds  of  hay  as  were  required  by  an 
equal  weight  of  corn  grain.  With  the  further  work  needed 
to  digest  it  and  excrete  the  wastes,  only  one  half  of  the  fuel 


THE  FEEDING  OF  ANIMALS  281 

value  digested  from  hay  is  left  for  "productive  fuel  value" 
in  the  animal. 

This  is  the  great  secret  as  to  why  grains  and  mill  feeds 
fatten  cattle  and  keep  horses  in  condition,  while  hay  alone 
will  not  do  so.  So  much  of  the  fuel  value  of  hay  is  used 
in  the  work  of  digestion  that  little  is  left  for  the  use  of  the 
animal.  There  may  be  enough  left  for  the  needs  of  the 
resting  animal,  but  when  there  is  work  to  be  done,  either  in 
fattening  or  in  muscular  effort,  grains  or  their  mill  products 
must  be  included  in  the  rations. 

Have  you  ever  wondered  why  animals  which  eat  hay 
are  not  fed  the  straws,  and  especially  wheat  straw?  Little 
productive  value  is  left  from  the  work  of  digesting  the 
straw.  For  a  resting  animal  2.4  pounds  of  wheat  straw 
are  equal  to  a  pound  of  corn  grain;  but,  when  work  is  re- 
quired, 8.6  pounds  of  it  are  necessary  to  replace  a  pound  of 
the  corn.  Such  a  feeding  stuff  hardly  repays  the  working 
animal  for  the  work  required  in  passing  it  through  his  body. 

The  Nutritive  Ratio.  A  scientific  basis  for  feeding 
animals  based  upon  the  principles  we  have  just  been  study- 
ing was  first  used  about  1864.  Half  a  century  before  that 
a  very  crude  standard  was  proposed  by  which  meadow 
hay  was  taken  as  the  basis  with  which  to  compare  different 
feeding  stuffs.  Probably  the  need  of  some  such  step  as  this 
had  been  realized  many  years  earlier.  We  owe  the  present 
method  of  measuring  the  values  of  feeding  stuffs  by  their 
digestible  food  compounds,  or  digestible  nutrients,  to  the 
German  scientist,  Dr.  Wolff.  A  great  deal  of  work  has  been 
done  by  many  investigators  of  nutrition  to  obtain  the  needed 
values  of  digestibility  of  the  nutrients  in  various  feeding 
stuffs.  One  of  the  most  interesting  facts  about  this  work  is 
that  it  shows  great  differences  between  the  digesting  power 
of  ruminant  and  non-ruminant  animals.  The  ruminants, 
as  we  might  expect,  from  their  more  complicated  stomach, 
have  the  greater  digestive  power.     For  example,  the  horse 


282  CHEMISTRY  OF  THE  FARM  AND  HOME 

digests  only  about  21  per  cent  of  the  protein  of  timothy  hay, 
while  the  cow  digests  about  47  per  cent.  For  the  carbo- 
hydrates other  than  cellulose,  or  the  nitrogen-free  extract, 
the  respective  percentages  are  47  and  62.  The  fat  differs 
in  the  same  way.  As  has  been  explained  before,  the  greater 
digestion  of  the  nutrients  by  ruminants  than  by  non-rum- 
inants is  due  chiefly  to  their  greater  power  to  digest  cellulose. 
This  difference  in  digestive  power  is  true  of  timothy  hay, 
for  cattle  digest  about  53%  of  the  crude  fibre  of  timothy 
hay,  while  horses  digest  only  43%  of  it.  In  expressing  the 
values  of  feeding  stuffs  their  digestible  part  is  treated  so 
as  to  compare  the  building  protein  compounds  with  the 
heating  fats  and  carbohydrates.  This  expression  is  called 
the  ''Nutritive  Ratio."  It  is  the  ratio  of  the  weight  of  di- 
gestible protein  to  the  combined  weight  of  the  other  digestible 
organic  compounds  expressed  as  fuel  value  of  carbohydrates. 
For  the  reason  already  explained,  fat  is  given  2.4  times  the 
value  of  carbohydrate  in  this  ratio.  The  numerical  value 
of  the  nutritive  ratio  is  found  by  the  following  proportion: 
Digestible  protein :  [digestible  carbohydrate  +  (2.4  X  diges- 
tible fat)]  =1:  X. 

We  can  calculate  the  nutritive  ratio  of  wheat  bran  for 
cattle  by  consulting  tables  of  digestibility  in  a  standard 
book  on  feeding,  such  as  Professor  Henry's.  In  such 
tables  we  shall  find  the  percentages  of  the  total  nutrients 
which  are  digestible  called  "Coefficients  of  Digestibility." 
The  percentage  of  the  total  protein,  fat,  nitrogen-free  extract 
and  fiber  in  wheat  bran  are  15.4;  4.0;  53.9,  and  9.0,  respec- 
tively. Of  these  total  amounts  in  100  pounds  of  the  feeding 
stuff  there  are  digested  by  cattle  the  following  percentages 
of  the  respective  constituents:  77.8,  68.0,  69.4,  and  28.6. 
Multiplying  the  total  per  cent  of  each  constituent  by  its 
percentage  of  digestibility  and  using  the  values  in  the 
proportion  just  given,  we  can  find  the  nutritive  ratio.  The 
crude  fiber  and  nitrogen-free  extract  are  combined  to  give 


THE  FEEDING  OF  ANIMALS  283 

the    value    for    carbohydrates.     Therefore    the    nutritive 
ratio  is: 
11.98:  [37.4+2.57+(2.4X2.72)]  =  11.98:  46.50.  =  1  :  3.88. 

This  is  a  "narrow''  ratio,  that  is  it  contains  a  high  ratio 
of  protein  to  fuel  value.  Barley  meal  has  the  ''medium" 
nutritive  ratio  of  about  1 : 8.  Timothy  hay,  on  the  other 
hand,  has  a  ratio  of  about  1 :  17,  which  is  regarded  as  ''wide." 
It  will  be  well  worth  while  for  you  to  calculate  the  nutritive 
ratios  of  other  kinds  of  feeding  stuffs,  such  as  oat  straw,  rut- 
abagas, and  linseed  meal.  Calculate  also  the  nutritive  ratio 
of  one  or  more  of  these  feeds  when  fed  to  the  horse  or  pig, 
and  compare  it  with  the  corresponding  value  for  cattle. 

A  narrow  nutritive  ratio  of  the  animal's  mixed  ration 
is  important  where  either  rapid  growth  or  the  production 
of  milk  is  required.  This  is  why  blood  meal  is  beneficial  to 
young  pigs,  oil  meal  to  calves,  and  cottonseed  meal  to  dairy 
cows.  For  maintaining  a  resting,  mature  animal,  feeding 
stuffs  of  wide  nutritive  ratio,  such  as  timothy  hay,  are 
sufficient.  For  fattening  purposes,  where  considerable  fuel 
value  and  a  moderate  amount  of  protein  are  required,  a 
medium  ratio  is  effective.  That  is  why  corn  meal  serves 
very  well,  as  you  may  have  learned,  for  fattening.  In  feeding 
practice  it  is  usual  to  vary  the  nutritive  ratio  from  1:4  for 
young  animals  to  1:12  for  resting,  mature  animals. 

Individual  Differences  in  Food  Requirement.  We  should 
remember  that  the  feeding  of  animals  is  quite  different  from 
performing  chemical  experiments.  In  a  chemical  experi- 
ment one  can  calculate  just  what  quantities  of  materials 
are  required  to  produce  a  given  amount  of  product.  Not 
so,  however,  with  feeding!  For,  though  the  use  of  the  food 
consists  largely  of  chemical  reactions,  the  latter  are  too 
numerous  and  complicated  to  permit  as  yet  calculation 
of  the  amounts  of  compounds  reacting.  Furthermore, 
the  living  animal  is  a  far  different  sort  of  reaction  vessel 
than  a  beaker  or  test  tube.     On  account  of  their  complex 


284  CHEMISTRY  OF  THE  FARM  AND  HOME 

mechanism,  no  two  individuals  give  just  the  same  results 
from  a  given  amount  of  feeding  stuffs.  Even  the  same 
animal  gives  different  results  at  different  times,  depending 
upon  the  continually  changing  condition  of  its  body.  So 
you  see  there  is  need  for  the  ''eye  of  the  master"  to  co-oper- 
ate with  the  scientific  principles  of  feedings. 

Mother's  Milk  a  Guide.  Nature's  choice  for  the  food 
of  the  young  animal  gives  man  a  scientific  basis  upon  which 
to  begin  feeding  when  weaning  is  done.  The  mother's  milk 
is  a  highly  specialized  food  balanced  in  composition  to  meet 
the  needs  of  the  rapidly  growing  body.  Chemical  analysis 
has  disclosed  the  important  fact  that  those  animals  whose 
young  mature  most  rapidly  produce  milk  richest  in  protein 
and  in  ash  constituents.  For  example,  the  ewe,  whose 
young  requires  fifteen  days  to  double  its  weight,  yields 
milk  containing  4.9  per  cent  of  protein  and  0.84  per  cent 
of  ash.  Woman,  on  the  other  hand,  whose  young  doubles 
its  weight  in  one  hundred  eighty  days,  or  twelve  times  the 
period  required  by  sheep,  produces  milk  which  contains 
only  1.6  per  cent  of  protein  and  0.2  per  cent  of  ash.     Since 


Figure  82.     Lack  of  phosphorus  in  their  rations  crippled  these  pigs  by 
weakening  their  bones. 

the  ash  of  milk  consists  largely  of  calcium  phosphate,  we 
see  here  emphasized  the  great  importance  of  this  compound 
and  of  protein  in  the  processes  of  building  muscle  and  skele- 


THE  FEEDING  OF  ANIMALS  285 

ton.  The  nutritive  ratio  of  milk  is  narrow.  It  ranges  from 
1 :  2  for  the  sow  to  1 : 4  for  the  cow.  It  is  important  in  feeding 
to  remember  that  the  mother  with  young  has  the  same 
sort  of  demands  to  supply  as  the  young  animal.  She  should, 
therefore,  receive  rations  containing  liberal  amounts  of 
protein,  calcium  and  phosphorus.  You  might  look  up  some 
tables  giving  the  composition  of  feeding  stuffs  and  select 
some  mill  products  you  would  recommend  for  her  ration. 
For  example,  clover  or  alfalfa  hay  is  especially  valuable 
as  a  source  of  calcium. 

Ash  Constituents.  Proper  kinds  and  amounts  of  ash 
constituents  are  very  important  in  the  food  of  animals. 
Sometimes  serious  trouble  comes  from  a  lack  of  either  phos- 
phorus or  calcium.  Pigs  fed  almost  entirely  on  corn  or  corn 
feeds  often  lose  the  use  of  their  legs.  At  first  their  hind 
parts  weaken  and  finally  they  are  unable  to  walk.  Corn 
grain  is  very  poor  in  calcium.  It  contains  a  good  deal 
of  phosphorus,  but  that  does  the  animal  little  good,  if  it 
gets  no  calcium  to  combine  with  it  for  making  calcium  phos- 
phate of  the  bones.  In  Hke  manner,  horses  fed  too  exclu- 
sively upon  grains  often  develop  a  porous  condition  of  the 
bones  called  ^'millers'  horse  disease'*  or  *'bran  rachitis.'' 
This  trouble  is  also  due  to  an  improper  ratio  between  calcium 
and  phosphorus  in  the  food.  There  are  in  a  molecule  of 
tricalcium  phosphate,  the  chief  constituent  of  bones,  three 
atoms  of  calcium,  each  having  an  atomic  weight  of  40. 
There  are  present  also  two  atoms  of  phosphorus,  each  with 
an  atomic  weight  of  31.  Thus  there  are  120  parts  of  calcium 
to  62  parts  of  phosphorus,  by  weight.  What  is  the  ratio 
of  calcium  to  one  part  of  phosphorus?  The  following 
are  the  ratios  of  calcium  to  one  part  of  phosphorus  in  the 
feeding  stuffs  named:  Corn  grain,  0.07;  oats  grain,  0.26; 
potatoes,  0.25;  turnips,  1.36;  meadow  hay,  3.72;  clover  hay, 
5.90;  alfalfa  hay,  7.84.  We  recall  here,  as  was  learned  in 
the  study  of  the  plant,  that  phosphorus  accumulates  in  the 


^88 


CHEMISTRY  OF  THE  FARM  AND  HOMB^ 


seeds  of  plants,  but  calcium  is  most  abundant  in  the  straws. 
Which  of  these  feeding  stuffs  would  you  select  to  make  up 
the  deficiency  of  the  corn  grain  in  calcium? 

The  fuel  needs  of  the  animal  are  measured  by  an  appara- 
tus called  the  respiration  calorimeter.  This  is  an  air-tight 
chamber  in  which  the  animal  can  be  confined,  and,  as  the 


Figure  83.  The  respiration  calorimeter  used  by  Dr.  Armsby  in  studying  the  food 
requirements  of  animals.  The  doors  at  the  left  show  how  the  walls  are  built  in 
separated  parts  to  prevent  the  loss  of  heat  to  the  outer  room.  Some  of  the 
apparatus  in  view  is  for  preparing  the  air  supplied  to  the  calorimeter  and  meas- 
uring the  gases  removed  from  it. 


name  indicates,  its  products  of  respiration  and  heat  pro- 
duction can  be  accurately  measured.  Analyzed  air,  con- 
taining a  proper  amount  of  water,  is  forced  into  the  chamber 
and  the  escaping  air  is  also  carefully  analyzed.  Very  slight 
changes  of  temperature  within  the  chamber  can  also  be 
measured  very  accurately.  One  of  the  important  find- 
ings of  this  apparatus  is  that  small  animals  require  more 


THE  FEEDING  OF  ANIMALS 


287 


fuel  value  in  their  food  per  pounds  of  their  weight  than 
do  large  animals.  From  your  study  of  soils  you  will  recall 
that  a  pound  of  clay  contains  more  surface  on  its  particles 
than  does  a  pound  of  coarse  sand,  because  small  spherical 
bodies  possess  more  surface  in  proportion  to  their  bulk  than 
large  ones.  The  same  fact  applies  to  animals.  On  account 
of  this  greater  proportion  of  surface  to  weight,  a  small 
animal  loses  more  heat  into  the  air  in  proportion  to  its  weight 
than  a  large  animal.  The  amount  of  heat  lost  from  a  square 
inch  of  body  surface  is  nearly  the  same  for  all  animals.  If 
we  select  the  dog  and  the  mouse  for  comparison,  both  animals 
being  at  rest,  we  shall  find  that  the  former  produces  only 
about  one  fifth  as  much  heat  per  pound  of  weight  as  the 
latter.  The  horse  produces  about  one  twentieth  as  much 
heat  per  pound  of  weight  as  the  mouse.  Thus  we  see  that 
young  and  small  animals  need  more  liberal  supplies  of 
carbohydrates  and  fat  than  mature  and  large  animals. 
The  rate,  or  severity,  of  labor  is  another  thing  which 

regulates  the  de- 
mand for  food. 
When  the  oxy- 
gen used  by  the 
animal  is  increas- 
ing, we  know 
that  more  fuel 
value  is  being 
required  of  the 
food.  The  great- 
er consumption 
of  oxygen  shows 
that  more  food 
is  being  burned 
in  the  body  tis- 
sues.   The  great 

Figure  84.     A  spirited  hackney.   His  movements  require        r^ 

energy  or  fuel  value  from  his  food.  Uerman     SCien- 


288      CHEMISTRY  OF  THE  FARM  AND  HOME 

tist,  Dr.  Zuntz,  has  devised  a  silver  tube  to  be  in- 
erted  in  the  trachea,  or  windpipe,  of  the  horse,  so  that 
the  oxygen  used  by  it  can  be  measured  readily.  By 
this  means  it  has  been  learned  that  increasing  the 
speed  over  a  given  distance  increases  the  amount  of  food 
required.  Changing  from  a  slow  walk  to  a  trot  three  times 
as  rapid  doubles  the  food  requirement.  Horses  of  high  ac- 
tion, such  as  hackneys  and  coaches,  which  do  much  work 
in  lifting  the  body,  require  especially  high  food  values. 
The  fact  that  this  action  increases  the  food  requirements 
explains  their  almost  insatiable  appetite  at  times. 

Need  of  Proteins.  Muscular  work  causes  a  destruction 
of  tissue,  which  must  be  repaired.  So  we  find  that  increase 
in  its  severity  increases  the  need  of  proteins  as  well  as  of 
carbohydrates  and  fats.  Besides,  especially  with  the  milch 
cow,  some  excess  of  protein  above  the  actual  need  for  repairs 
is  necessary  for  the  best  results.  Protein  seems  to  act  in 
some  way  as  a  tonic  stimulating  the  milk-producing  cells 
and  other  cells  of  the  body  to  their  best  efforts. 

Special  Needs.  The  special  products  of  some  animals 
create  special  needs  in  feeding.  Wool,  eggs  and  milk,  on 
account  of  the  large  proportion  of  proteins  in  their  compo- 
sition, require  narrow  nutritive  ratios  for  the  rations  of  the 
animals  producing  them.  Wool  is  nearly  pure  protein. 
The  soUds  of  milk,  that  part  left  by  drying,  are  over  one 
fourth  protein  and  those  of  eggs  are  about  one  half  protein. 
The  hard-working  milch  cow  does  best  on  a  nutritive  ratio 
of  about  1:6.5.  Young  pasture  grass,  whose  beneficial 
effect  on  the  flow  of  milk  is  well  known  to  farmers,  has  a 
ratio  narrower  than  this.  It  would  be  interesting  to  know 
how  much  of  its  food  so  complicated  a  machine  as  the  milch 
cow  uses  for  different  purposes.  Director  Jordan,  of  the 
New  York  State  Experiment  Station,  has  estimated  that 
about  one  third  of  the  fuel  value  of  this  animal's  ration 
is  required  to  maintain  her  body  and  one  third  is  contained 


THE  FEEDING  OF  ANIMALS 


289 


in  the  organic  compounds  of  the  milk.  The  remaining 
third  of  the  fuel  value  is  used  in  the  work  of  producing  the 
milk.     Do  you  not  see  herein  very  good  reasons  why  the 


Figure  85.  A  high  grade  cow  and  her  year's  production 
of  butter.  She  is  the  most  efficient  producer  among 
the  farm  animals. 


dairy  cow  giving  milk  should  receive  oil  meal,  wheat  bran  and 
other  concentrated  mill  feeds? 

Working  or  producing  animals  are  like  long  distance 
runners  on  the  track  team  in  this  respect,  that  it  is  the  final 
stages  of  their  efforts  that  cost  the  most  energy.  Tired 
muscles  and  cells  work  less  efficiently  than  fresh  ones. 
For  this  reason  the  last  few  seconds  clipped  from  a  trotting 


n 

PI 

pp 

PPH 

m 

f  ■"""■■; ^ 

I    J 

1       1 

PTTl 

"""^  ^fc'iV-'^'-'iB 

r-^ 

1  >-  i  J 

m.A  ■'-■'-■^^^ 

.  ^^^bC^K'v 

m 

m 

^M^H 

Jm^^B'^  rl^  rB 

li 

Figure  86. 


19— 


A  prolific  hen  and  her  product  of  five  years, 
lower  than  that  of  the  cow. 


Her  efficiency  is  much 


290      CHEMISTRY  OF  THE  FARM  AND  HOME 

record  and  the  last  few  pounds  of  butter-fat  in  a  record- 
breaking  production  cost  much  more  in  protein  and  fuel 
value  than  the  same  amounts  of  products  from  moderate 
work.  It  requires  an  extra  allowance  of  food  to  support 
these  extraordinary  efforts.  The  feeder  who  desires  them 
must  exercise   special   skill. 

Feeding  Standards.  Dr.  Armsby,  of  the  Pennsylvania 
Experiment  Station,  has  spent  many  years  in  studying 
the  food  requirements  of  animals  by  the  use  of  the  respira- 
tion calorimeter.  Professor  Haecker,  of  the  Minnesota 
Experiment  Station,  has  made  a  thorough  study  of  the  food 
requirements  of  the  dairy  cow.  We  ought  to  know  some- 
thing about  the  lessons  which  these  men  have  learned.  It 
is  not  necessary  to  burden  our  mind  with  remembering  the 
different  amounts  of  food  values  which  they  recommend. 
It  is  important,  however,  for  us  to  remember  the  scientific 
principles  which  they  teach. 

For  a  resting  horse  weighing  1,250  pounds,  Dr.  Armsby 
proposes  0.6  pounds  of  digestible  protein  in  the  food  daily. 
When  the  animal  is  doing  light  work  he  recommends  that 
1  pound  of  the  protein  be  fed.  For  heavy  work  he  raises 
the  amount  to  2  pounds.  He  recommends  raising  the  fuel 
value  at  the  same  time  from  7.0  to  9.8  to  16.0  therms  daily, 
as  the  work  of  the  animal  increases.  There  are  two  facts 
which  you  will  see  very  plainly,  if  you  will  compare  these 
different  values.  The  first  of  these  facts  is,  that,  with  in- 
crease of  work,  the  need  for  protein  increases  more  rapidly 
than  that  for  fuel  value.  The  second  is  that  both  of  these 
needs  increase  rapidly  as  the  amount  of  work  increases. 
For  growing  cattle  Dr.  Armsby  recommends  1.0  pound  of 
digestible  protein  and  4.5  therms  of  fuel  value  daily  when 
the  animal  weighs  250  pounds.  A  two-year-old  weighing 
about  1,000  pounds  should  receive  1.75  pounds  of  protein 
and  8.6  therms.  The  important  fact  readily  seen  here  is 
that  the  food  requirements  of  the  animal  do  not  increase 


THE  FEEDING  OF  ANIMALS  291 

nearly  as  fast  as  its  weight.  While  the  body  weight  has 
increased  four-fold  in  this  example,  the  protein  and  fuel 
value  required  have  not  even  doubled.  For  a  milch  cow 
weighing  about  1,000  pounds,  Professor  Haecker  recommends 
0.7  pound  of  digestible  protein  and  7.2  pounds  of  digestible 
carbohydrates  and  fat  daily  to  support  the  animal.  To 
this  he  adds  .054  pound  of  protein  and  .29  pound  of  carbo- 
hydrates and  fat  for  each  pound  of  milk  produced  containing 
4  per  cent  of  butter-fat.  He  recommends  increasing  the 
food  of  this  mature  animal  with  its  special  kind  of  work 
very  nearly  at  the  same  rate  as  its  weight  and  its  product 
increase.  This  shows  that  different  kinds  of  animals  re- 
quire different  care  in  feeding.  The  good  farmer  must, 
indeed,  be  one  of  the  wisest  of  men. 

Influence  of  Food.  Like  the  plant,  the  animal  body 
grows  to  its  final  chemical  composition  quite  independent 
of  influence  by  the  composition  of  its  food.  Experiments 
have  been  carried  out  in  which  young  animals  as  nearly 
alike  as  they  could  be  chosen  were  fed  in  some  cases 
upon  narrow  nutritive  ratios  and  in  other  cases  upon  wide 
ones.  These  experiments  have  shown  that  narrow  rations 
produce  somewhat  more  rapid  growth  and  larger  organs 
than  do  wide  ones.  The  chemical  composition  of  the 
body,  however,  is  regulated  by  inheritance.  Even  environ- 
ment does  not  control  the  animal  by  the  power  which  we 
have  learned  it  has  to  mold  the  composition  of  the  plant. 
The  composition  remains  the  same  for  a  given  kind  of  animal, 
whatever  be  the  nature  of  its  food. 

Condimental  feeding  stuffs  are  materials  advertised 
upon  the  market  with  all  sorts  of  wonderful  claims.  Some 
are  recommended  as  tonics  and  others  as  special  fattening 
foods.  They  are  usually  made  from  some  common  mill 
product  such  as  wheat  middlings  or  linseed  meal.  Com- 
mon, inexpensive  tonic  substances  like  ferrous  sulphate 
and  such  laxatives  as  sodium  sulphate  or  magnesium  sulphate 


292 


CHEMISTRY  OF  THE  FARM  AND  HOME 


are  added.  Those  prepared  for  poultry  generally  contain 
ground  oyster-shell  or  bone  to  furnish  calcium  for  eggshells. 
They  are  sometimes  deceptively  colored.  These  feeding 
stuffs  are  commonly  sold  in  small  packages  at  prices  many 
times  their  true  values.  The  farmer  should  realize  that 
their  simple  ingredients  are  sold  at  unreasonable  prices. 


Figure  87.  A  chemical  laboratory  of  a  state  experiment  station.  Here  the  values 
of  commercial  feeding  stuffs  are  determined.  Commercial  fertilizers  are  also 
inspected  here.     This  work  protects  the  farmers  who   purchase  these  materials. 

He  should  also  realize  that  tonics  cannot  increase  the  work 
done  by  healthy,  well-fed  animals.  If  live  ntock  need  medi- 
cal treatment,  it  is  cheaper  and  safer  to  consult  a  veteri- 
narian than  to  experiment  with  condimental  feeding  stuffs. 
Feeding  Stuff  Laws.  Purchase  of  feeding  stuffs  of  all 
sorts  is  made  safe  for  the  farmer  by  the  protection  of  the 
law.  The  experiment  station  is  responsible  for  enforcing 
the  feeding  stuff  laws.  Manufacturers  are  required  to  label 
their  goods  plainly  with  a  guarantee  of  their  composition 
and  Experiment  Station  agents  are  empowered  to  sample 


THE  FEEDING  OF  ANIMALS  293 

and  analyze  the  products  exposed  for  sale.  Violators  of 
the  law  are  prosecuted  and  only  trustworthy  brands  are 
allowed  to  remain  on  the  market.  This  protective  legis- 
lation and  the  results  of  the  feeding  stuff  inspection  published 
in  bulletins  of  the  Experiment  Station  protect  the  farmer 
in  getting  what  he  pays  for. 

SUMMARY 

Knowledge  of  the  composition  of  feeding  stuffs  and  how  they  serve 
the  animal  is  the  basis  of  scientific  feeding.  Protein  compounds, 
most  abundant  in  grains  and  in  hays  of  legume  plants,  serve  for  growth 
and  repair.  Fats,  which  occur  chiefly  in  grains,  and  digestible  carbo- 
hydrates, abundant  in  grains,  are  either  used  as  fuel  or  stored  as  fat. 
By  means  of  the  bomb  calorimeter  the  fats  have  been  found  to  contain 
2.4  times  as  much  fuel  value  as  the  carbohydrates.  This  fuel  value 
is  measured  in  units  called  Calories  and  therms. 

Only  part  of  the  fuel  value  of  feeding  stuffs  is  finally  of  use  to  the 
animal.  This  result  is  due  to  losses  during  digestion.  Crude  fiber, 
a  mixture  of  cellulose  compounds,  which  amounts  to  nearly  one  third 
of  the  material  in  some  hays,  is  largely  responsible  for  these  losses. 
As  a  result,  the  producing  value  ranges  from  0.4  of  the  total  fuel  value 
in  some  grains  and  mill  products  to  only  0.06  of  the  total  in  some  straws. 
The  importance  of  grain  to  milch  cows,  growing  animals  and  working 
horses  is  thus  explained. 

The  present  scientific  standard  for  comparing  feeding  stuffs 
balances  the  digestible  proteins  against  the  digestible  carbohydrates 
and  fats  in  an  expression  called  the  nutritive  ratio.  The  nutritive 
ratio  should  vary  from  narrow,  or  about  1:5  for  young  animals  and 
milch  cows  to  wide,  or  about  1:12   for  resting,  mature  animals. 

The  amounts  of  protein  compounds  and  fuel  value  increase 
rapidly  as  the  muscular  work  of  the  animal  increases.  The  need  for 
them  in  growth  does  not  increase  nearly  as  rapidly  as  the  size  of  the 
animal.  By  inclosing  the  animal  in  a  respiration  calorimeter  his  fuel 
need  can  be  measured.  On  account  of  the  greater  proportion  of  sur- 
face to  weight  this  need  is  greater  for  small  than  for  large  animals. 
The  composition  of  the  feeding  stuffs  influences  the  rate  and  amount 
of  growth  but  not  the  composition  of  the  animal. 

In  the  purchase  of  feeding  stuffs  the  farmer  has  the  help  and 
guidance  of  the  Experiment  Station,  which  executes  state  laws  con- 
trolling the  sale  of  these  things. 


294  CHEMISTRY  OF  THE  FARM  AND  HOME 

QUESTIONS 

1.  Under  what  six  groups  does  the  chemist  class  the  compounds 
of  feeding  stuffs  by  analysis? 

2.  How  much  water  is  there  in  a  fresh  turnip?      In  cured  hay? 

3.  How  much  protein  is  there  in  mangels?     In  clover  hay? 

4.  What  is  the  difference  between  the  ether  extract  of  grains 
and  that  of  hays? 

5.  What  is  the  nature  of  crude  fiber?     How  much  in  hays? 

6.  What  is  the  chief  compound  of  the  nitrogen  free  extract  of 
grains? 

7.  How  much  ash  is  there  in  feeding  stuffs? 

8.  Of  what  use  is  protein  to  the  animal? 

9.  For  what  are  carbohydrates  and  fats  used? 

10.  For  what  purpose  is  the  bomb  calorimeter  used? 

11.  What  is  a  calorie? 

12.  Which  are  the  more  efficient  in  supplying  energy  to  the 
body,  carbohydrates  or  fats?     Why? 

13.  Name  two  materials  in  which  unused  fuel  value  of  the  food 
leaves  the  animal  body. 

14.  What  is  meant  by  the  "productive  fuel  value"  of  feeding 
stuffs? 

15.  Which  has  the  greater  productive  value,  cornmeal  or  timothy 
hay?     Why? 

16.  What  is  the  nutritive  ratio? 

17.  When  is  the  nutritive  ratio  narrow?     For  what  animals  is 
such  a  ratio  desirable? 

18.  Will  animals  of  like  kind  and  size  necessarily  have  like  food 
requirements?     Why? 

19.  What  relation  is  there  between  the  composition  of  the  milk 
and  the  growth  of  the  young  of  different  species? 

20.  Why   does   the  young   animal   require   a   narrow   nutritive 
ratio? 

21.  What  is  the  danger  from  feeding  young  pigs  too  exclusively 
on  com?     What  feeding  stuffs  will  correct  the  trouble? 

22.  Why  does  the  small  animal  require  more  fuel  value  than 
the  large  one  in  proportion  to  body  weight? 

23.  What  is  the  effect  of  rate  of  work  on  the  food  requirement? 

24.  Which  increases  the  more  rapidly,   protein   or  fuel   need? 

25.  What  are  the  objections  to  condimental  feeding  stuffs? 

26.  What  are  the  benefits  of  the  state  laws  regarding  feeding 
stuffs? 


CHAPTER  XII 
DAIRY  PRODUCTS 

Importance  of  Dairying.  There  are  three  C's  important 
in  dairy  farming.  Have  you  ever  heard  of  them?  They 
occur  in  these  three  words:  Clover — Corn — Cows.  Wher- 
ever clover  hay  and  ensilage  corn  thrive  you  may  expect  to 
find  prosperous  farmers.  Having  already  studied  the 
first  two  of  these  C's  we  can  concentrate  our  attention  upon 
the  milch  cow  and  her  products. 

The  amount  of  dairy  farming  in  the  United  States  has 
increased  rapidly  in  recent  years.  This  is  partly  due,  of 
course,  to  the  enlarging  food  needs  of  our  rapidly  increasing 
population.  At  present,  the  yearly  value  of  dairy  products 
for  a  single  state,  Wisconsin,  exceeds  the  huge  sum  of  $100,- 
000,000.  In  the  manufacture  of  the  various  products  from 
milk  very  complex  physical  and  chemical  changes  occur. 
To  put  out  these  products  from  day  to  day  always  of  high 
quality  requires  no  small  skill  of  the  dairyman.  He  must 
properly  control  the  conditions  which  influence  these  com- 
plex changes.  Knowledge  of  chemical  principles  can  help 
him  greatly.  As  possible  future  dairymen  we  shall  now  con- 
sider the  most  important  physical  and  chemical  processes 
related  to  the  handhng  of  milk  and  its  products. 

The  Udder.  Milk  is  the  fluid  produced  for  feeding  the 
young  by  special  organs  of  the  mother  among  that  class 
of  animals  known  as  mammals.  The  milk  glands  of  the 
cow,  called  the  udder,  have  been  developed  to  great  capacity 
by  man  through  selective  breeding.  Have  you  seen  the 
equal  of  the  udder  of  the  cow  shown  in  Figure  88?  When 
the  calf  has  been  born,  and  no  longer  receives  food  directly 
from  the  mother's  blood  stream,  the  blood  is  turned  in  great 

295 


296 


CHEMISTRY  OF  THE  FARM  AND  HOME 


currents  through  the  blood  vessels  of  the  udder.  By 
their  peculiar  and  wonderful  powers  the  cells  of  this  organ 
draw  upon  the  one  side  from  the  compounds  of  the  blood 
and  secrete  upon  the  other  side  the  valuable  food  fluid 
called  milk.  The  watei  and  salts  of  the  blood  are  used  in 
this  process  pretty  much  unchanged.  The  organic  com- 
pounds of  the  blood,  however,  are  rapidly  rebuilt  to  quite 


Figure  88.  Friderne  Pride  Johanna  Rue,  world's  champion  of  1914.  Besides  being 
an  animal  of  sensitive  temperament  she  is  a  wonderful  machine  that  produced 
1,146.47  lbs.  of  butter-fat  in  one  year. 

different  compounds  which  appear  in  the  milk.  Figure  89 
shows  how  thickly  masses  of  these  cells  fill  the  upper  part  of 
the  udder.  Even  here,  however,  there  are  minute  spaces 
between  many  of  the  cells,  which  can  be  seen  under  the 
microscope.  These  spaces  join  to  form  larger  and  larger 
cavities  which  finally  empty  into  the  cistern  above  the  teat. 
Specific  Gravity  of  Milk.  Milk  weighs  a  little  more  than 
water  on  account  of  some  of  the  compounds  which  it  con- 
tains. While  water  weighs  1,000  grams  to  the  liter  milk 
weighs  1,031  grams.  In  other  words,  average  milk  is  1.031 
times  as  heavy  as  water.    Learn  from  some  help  the  mean- 


DAIRY  PRODUCTS 


297 


ing  of  specific  gravity.  The  specific  gravity  of  milk  is  very 
nearly  1.031  on  the  average.  There  is  an  instrument  called 
the  lactometer  which  shows  by  the  depth  to  which  it  sinks 
whether  the  milk  has  been  skimmed  or  watered.  With 
whole  milk  this  instrument  sinks  to  a  marked  point  on  its 
scale.  The  removal  of  fat,  the  lightest  constituent  of  the 
milk,  by  skimming  increases  the  weight  of  the  milk.     Will 

the  lactometer  sink  more 
or  less  than  in  unskim- 
med milk?  If  water 
weighs  less  than  milk 
how  will  watering  of  the 
milk  affect  the  depth  to 
which  the  lactometer 
sinks?  The  lactometer 
cannot  give  any  protec- 
tion against  fraud  so  cer- 

Figure  89.     Section  through  a  cow's  udder.         ,     .  ,^      ,       r      i  •      i 

tarn  as  that  of  chemical 
analysis. 

The  opacity  of  milk  and  its  whiteness  are  due  to  particles 
suspended  in  it  which  reflect  the  light. 

The  chemical  composition  of  milk  is  far  from  simple. 
In  simplest  terms,  however,  we  may  say  that  it  consists 
of  a  mixture  of  true  solution,  colloidal  solution  and  emulsion. 
From  this  we  see  that  water  is  very  important  in  the  com- 
position of  milk.  Water  forms  about  87  per  cent  of  the 
material  in  milk.  It  is  readily  driven  off  at  the  temperature 
of  boiling  water.  The  remaining  solid  matter  is  called 
"total  solids"  by  the  analyst. 

Lactose,  a  sugar,  forms  about  5  per  cent  of  the  milk 
or  0.4  of  the  total  solids.  This  sugar  belongs  to  the  same 
group  of  carbohydrates  as  sucrose  and  maltose.  It  is  found 
only  in  milk.  Right  here  the  remarkable  power  of  the 
udder  cells  is  shown.  They  receive  dextrose  as  the  only 
sugar  in  the  blood  and  produce  this  quite  different  com- 


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CHEMISTRY  OF  THE  FARM  AND  HOME 


pound,  lactose,  in  the  milk.  Lactose  is  quite  soluble  in 
water,   but  not  very  sweet. 

Fat  follows  sugar  in  abundance  in  the  milk.  It  forms 
about  4  per  cent  of  the  milk  or  0.3  of  the  solids.  Its  amount 
is  quite  different,  however,  for  different  breeds  of  cows.. 
The  other  constituents  do  not  show  nearly  so  great  dif- 
ferences. Some  animals  produce  milk  very  rich  in  fat. 
Elephant  milk  contains  about  20  per  cent 
and  the  milk  of  the  porpoise  and  whale  40 
to  50  per  cent.  Figure  91  shows  that  under 
a  microscope  the  fat  can  be  seen  scattered  in 
droplets  throughout  the  milk.  This  sus- 
pended condition  of  matter  is  called  an 
emulsion. 

Milk  fat  is  not  a  single  compound  but  a 
mixture  of  several  different  fats.  A  num- 
ber of  different  fatty  acids  are  united  with 
glycerine  in  these  fats.  On  the  one  hand 
are  the  acids  with  large  molecules,  such  as 
oleic,  which  we  studied  in  connection  with 
the  plant  and  the  animal.  On  the  other 
hand  are  fatty  acids  with  molecules  only 
one  fourth  as  large  as  this.  These  acids  are 
Figure  90.  The  lac-  Volatile  Hquids  with  peculiar,  sharp  odors, 
i?float[ng"in sau  Hke  the  acetic  acid  of  vinegar.  When  the 
lame'specificgrav-  buttcr  bccomcs  rancid,  these  acids  are  set 
ityasmiik.  ^^.^^    ^^^    produce    a    disagreeable    odor. 

They  are  important  in  distinguishing  butter  from  oleo- 
margarine. One  of  the  most  abundant  of  these  acids  is 
called  butyric  acid  Olein,  which  is  liquid  at  common 
temperature,  forms  about  one  third  of  milk  fat.  Over  one 
half  of  the  fat  is  made  up  by  individual  fats  which  are 
solid  at  common  temperatures.  Myristinand  palmitin  are 
the  chief  of  these.  The  remaining  liquid  fats,  containing 
the  volatile  fatty  acids,  form  about  one  tenth  of  the  fat. 


DAIRY  PRODUCTS  299 

Upon  the  ratio  of  solid  to  liquid  fats  depends  the  melt- 
ing point  of  the  milk  fat  or  butter.  How  will  the  rise 
and  fall  of  the  amount  of  olein  affect  the  melting  point  of 
the  butter? 

Proteins  rank  third  in  order  of  abundance  among  the 
compounds  of  milk.  They  form  about  3.3  per  cent  of  the 
milk  or  one  fourth  of  the  total  solids.  Casein  alone  forms 
about  four  fifths  of  the  milk  proteins. 
This  protein  contains,  besides  carbon, 
hydrogen,  oxygen  and  nitrogen,  0.8 
per  cent  each  of  sulphur  and  phos- 
phorus. It  is  not  truly  dissolved,  but 
exists  in  the  very  finely  divided  form 
of  a  colloidal  solution.  When  acid  is 
added  to  the  milk,  casein  separates  as 
a  curd.  Rennet  extract  prepared  from 
Figure  91.    Fat  globules  as  calvcs  stomach    also    coagulates    the 

seen    in    a    thin    layer    of  .  n  .  i 

milk    under    the     micro-    CaSClU,     Or,     aS     WC     Say,     CUrdlCS     the 

milk.  The  active  agent  of  this 
extract  is  the  enzyme  rennin.  Have  you  noticed  the  wrink- 
led scum  which  forms  on  the  surface  of  boiling  milk?  It  is 
casein  which  has  been  made  insoluble  by  partly  drying. 
Lactalbumin  is  another  protein  of  milk.  Only  about  0.7  per 
cent  is  present  in  common  milk.  It  coagulates  and  separ- 
ates in  flakes  when  the  milk  is  heated  to  72°C.  In  col- 
ostrum,  the  milk  produced  directly  after  calving,  there  is  12 
or  13  per  cent  of  lactalbumin.  This  causes  the  whole  of  the 
milk  to  clot  when  it  is  heated.  There  are  other  proteins 
present  in  very  small  amounts  in  milk,  but  the  only  one 
we  need  to  remember  is  fibrin.  This  resembles  blood  fib- 
rin by  separating  from  the  liquid  as  minute,  invisible 
threads,  which  may  entangle  the  fat  globules. 

Inorganic  salts  form  most  of  the  remainder  of  the  solids 
of  milk.  They  amount  to  about  0.7  per  cent  of  the  milk  or 
one  twentieth  of  the  total  solids.     Among  these  salts  the 


30C 


CHEMISTRY  OF  THE  FARM  AND  HOME 


chief  bases  rank  as  follows:  Potassium  oxide  forms  one 
fourth,  calcium  oxide  one  fifth  and  sodium  oxide  one  tenth 
of  the  milk  ash.  Of  the  acid  radicles  phosphorus  oxide 
forms  about  one  fourth  and  chlorine  one  seventh  of  the  ash. 
From  these  values  it  has  been  found  that  potassium  and 
calcium  phosphates  and  sodium  chloride  are  the  chief  salts 
present  in  milk.  Traces  of  the  iron  compounds  necessary 
for  the  growth  of  the  young  are  not  lacking.  The  calcium 
phosphate  is  closely  associated  with  casein.  Calcium  is 
important  in  the  action  of  rennin. 

Comparison  of  Milk  of  Different  Animals.  It  will  be 
interesting  to  compare  with  cow's  milk  the  composition  of 
the  milks  of  other  animals  commonly  used  as  human  food. 
The  comparison  is  given  in  Table  X. 

Table  X — The  Composition  of  Some  Common  Milks 


Fat 

Casein 

Lactose 

Ash 

% 

% 

% 

% 

Woman 

3.3 

1.5 

6.8 

0.2 

Cow 

3.9 

2.5 

5.1 

0.7 

Goat 

6.5 

4.3 

5.0 

0.7 

Camel 

2.9 

3.8 

5.7 

0.6 

How  do  the  amounts  of  casein  and  ash  in  woman's  milk 
compare  with  those  of  cow's  milk?  What  one  constituent 
is  more  abundant  in  woman's  milk  than  in  any  of  the  others? 
Notice  the  high  percentage  of  fat  and  casein  in  goat's  milk. 
In  recent  years  this  milk  has  been  recognized  as  very  nutriti- 
ous. The  figures  of  the  table  are  the  average  values  for  a 
number  of  different  samples.  We  should  find  them  con- 
siderably greater  or  less  for  different  animals. 

Comparison  of  Milk  of  Different  Breeds.  Cows  have 
different  compositions  of  the  milk  for  different  breeds. 
Only  the  fat  and  casein,  however,  differ  much  in  the  different 
breeds.  For  some  of  the  more  common  dairy  breeds  the 
average  percentages  of  fat  and  of  casein  are  as  follows : 


DAIRY  PRODUCTS 


301 


■--87% 


Holstein,  casein,  2.2  and  fat  3.3;  Ayrshire,  casein,  2.5  and 
fat  3.8;  Guernsey,  casein,  2.9  and  fat  5.4;  Jersey,  casein, 
3.0  and  fat  5.8.  You  will  see  that  fat  and  casein  increase 
together  in  passing  from  the  Holsteins  to  the  Jerseys.  Divide 
the  fat  of  the  Jersey  milk  by  that  of  the  Holstein.  Do  the 
same  with  the  casein.  Which  differs  most  widely  in  the 
two  milks?     We  should  remember  that  richer  milk  does 

not  necessarily  stamp 
the  Jersey  cow  as  su- 
perior to  the  Holstein. 
The  latter  may  produce 
so  much  larger  flow  than 
the  former  as  to  yield 
even  more  of  the  valu- 
able milk  solids. 

Influence  of  Lacta- 
tion Period.  The  milk 
of  any  one  cow  varies  in 
composition  at  different 
times.  This  is  due  chiefly 
to  two  causes:  (1)  the 
length  of  time  she  has 
been  in  milk;  and  (2)  the 
kind  of  feeding  stuffs  she 
receives.  The  length  of 
time  after  calving  is 
called  the  ''lactation  per- 
iod.'* About  ten  days  after  calving  the  colostrum  changes 
to  milk.  During  about  the  second  month  of  lactation  the 
milk  becomes  a  little  poorer  in  fat  and  other  solids  than  at 
first.  Then  it  gradually  increases  in  richness  and  after 
four  months  of  lactation  its  composition  becomes  richer 
than  at  first.  After  that  it  continues  to  increase  slowly  in 
richness.  This  richness  of  the  milk  at  late  stages  of  milk- 
ing is  due  to  the  fact  that  it  becomes  more  concentrated  in 


Figure  92.     Composition  of  whole  milk. 


302 


CHEMISTRY  OF   THE  FARM  AND  HOME 


total  solids.  No  one  constituent  increases  alone;  but  fat, 
casein  and  the  other  solids  increase  together  and  equally. 
What  is  really  happening  is  that  less  water  is  being  secreted 
into  the  milk.  Have  you  not  observed  that  the  ''flow"  or 
volume  of  milk  does  decrease  as  the  period  of  milking 
increases  and  the  cow  approaches  dryness? 

Influence  of  Feeding  Stuffs.  The  amount  of  feeding 
stuffs  received  has  no  effect  on  the  composition  of  the  milk 
of  well-fed  cows.  If  the  animals  are  poorly  fed,  however, 
they  cannot  do  their  best  work  in  milk-making.  They  will 
produce  richer  milk  when  well  fed.  Sudden  changes  of 
ration  also  affect  the  composition  of  the  milk.  Cows  fed 
on  feeding  stuffs  containing  only  a  moderate  amount  of  fat 

will  produce  milk  con- 
taining more  fat,  if  a 
ration  richer  in  fat  is 
fed  to  them.  A  change 
to  pasture  grass  from 
winter  feeding  acts  in 
this  way,  and  farmers 
are  glad  to  see  sum- 
mer pasturing  come 
around.  These 
changes  are  tempor- 
ary, however.  Milk 
and  seeds  are  much 
alike  in  this  respect, 

Figure  93.     Showing  the  effect  of  fat  from  differ-     that  the  COW    and    the 
ent  plants  upon  the  hardness  of  butter-fat.  i       j_    j.  i  • 

plant  try  always  to 
put  out  a  product  of  uniform  composition.  So,  each  cow's 
milk  soon  returns  to  a  composition  natural  for  her  after 
any  sudden  changes  of  her  rations. 

The  composition  of  the  fat  in  milk  can  be  changed  by 
changing  the  feeding  stuff.  Corn  oil  and  feeding  stuffs  rich 
in  it,  such  as  gluten  feed,  produce  soft  fat  in  the  milk.     On* 


DAIRY  PRODUCTS  303 

the  other  hand  cottonseed  meal  produces  hard  fat,  which 
is  soHd  at  ordinary  room  temperatures.  Can  you  not  see 
the  importance  of  this  property  of  feeding  stuffs  in  butter- 
making?  The  feeding  stuffs  act  in  this  way  by  affecting 
the  ratio  of  sohd  to  Hquid  fats  which  enter  the  composition 
of  the  milk  fat. 

The  Gases  of  Milk.  Milk  always  contains  gases.  There 
are  about  85  c.c.  of  gases  in  one  liter  of  freshly  drawn  milk; 
that  is,  the  separated  gases  would  equal  about  one  twelfth 
the  volume  of  the  milk.  Carbon  dioxide  forms  nine  tenths  of 
this  volume  of  gases.  When  the  milk  stands  in  open  pails 
much  of  this  carbon  dioxide  escapes  rapidly  to  the  air  and 
is  replaced  by  oxygen  and  nitrogen.  What  really  happens 
is  a  balancing  of  gases  between  the  air  and  the  milk.  Any 
odorous  gaseous  substances  in  the  air  also  enter  the  milk. 
Such  odorous  compounds  escape  from  manure  and  from 
turnips  and  other  vegetables.  To  avoid  a  bad  flavor  from 
these  substances  the  milk  should  be  removed  from  the 
stable  to  the  milk  room  as  soon  as  it  is  drawn. 

Decomposition  of  milk  takes  place  very  readily.  This 
is  because  its  soluble  organic  compounds  are  excellent  food 
for  bacteria.  These  organisms  are  always  floating  in  the 
air  and  are  sure  to  get  into  the  milk.  If  the  milk  is  kept  cold 
in  a  refrigerator,  they  act  only  very  slowly.  At  summer  heat, 
however,  they  multiply  rapidly  and  soon  spoil  the  milk. 
The  lactic  acid  bacteria  are  the  most  active  of  these  organ- 
isms. They  obtain  energy  for  life  and  growth  by  splitting 
lactose.  From  one  molecule  of  the  sugar  they  produce 
four  molecules  of  lactic  acid.  When  0.6  or  0.7  per  cent  of 
this  acid  has  accumulated,  it  causes  the  casein  to  coagulate. 
As  we  say,  ''it  curdles"  or  ''clabbers"  the  milk.  It  generally 
does  not  increase  to  more  than  about  1.0  per  cent  of  the 
milk.  This  amount  clogs  the  machinery  of  chemical  re- 
actions by  which  the  bacteria  act.  From  what  has  been 
said  you  can  see  the  importance  of  cooling  the  fresh  milk 


304  CHEMISTRY  OF   THE  FARM  AND  HOME 

quickly,  if  it  is  to  be  kept  sweet  for  a  while.  There  are 
special  pieces  of  dairy  machinery  for  cooling  by  means  of 
running  water.  Milk  can  also  be  kept  sweet  by  pasteuriza- 
tion. This  process  is  named  from  the  great  French  biologist 
Pasteur,  who  discovered  the  nature  and  importance  of 
bacteria.  By  heating  the  milk  thirty  minutes  at  70°C.  or 
158°F.  the  bacteria  are  killed.  The  vessel  must  then  be 
sealed  to  prevent  entrance  of  more  live  bacteria.  Un- 
scrupulous persons  have  sometimes  used  chemical  preserva- 
tives to  keep  milk  sweet  and  wholesome  in  appearance. 
Borax,  formalin  and  other  substances  have  been  used  for 
the  purpose.  In  the  amounts  necessary  for  effectiveness 
such  substances  are  positively  dangerous  to  the  health  of 
the  public.  The  use  of  most  of  them  is  now  prohibited 
by  law. 

Condensed  milk  and  milk  powder  are  forms  in  which 
milk  is  prepared  both  to  improve  its  keeping  qualities  and 
to  decrease  the  expense  of  shipping  it.  The  first  of  these 
products  is  made  by  evaporating  the  milk  in  a  partial 
vacuum.  How  does  the  vacuum  affect  the  usual  boiling 
temperature?  It  prevents  browning  the  lactose  by  over- 
heating it.  Sometimes  sucrose  is  added  as  a  preservative. 
Milk  powder  is  formed  by  spraying  milk  either  upon  hot 
steel  rollers  or  into  a  chamber  of  hot  air.  In  this  way  it 
is  converted  to  a  flaky  powder.  As  fat  prevents  the  ready 
evaporation  of  the  water,  it  is  necessary  to  partly  skim  the 
milk  before  it  can  be  well  dried.  For  this  reason  the  ratio 
of  fat  to  the  other  solids  may  be  lower  in  milk  powder 
than  in  whole  milk. 

Cream  consists  chiefly  of  milk  fat  together  with  small 
amounts  of  milk  proteins,  lactose  and  salts.  It  separates 
from  standing  milk  by  tlie  process  known  as  creaming. 
Twenty-five  years  ago  it  ^as  still  common  practice  among 
New  England  farmers  to  expose  the  milk  in  shallow  tin  pans 
at  about  15.5°C.  to  allow  the  cream  to  ''rise."      This  pro- 


DAIRY  PRODUCTS  305 

cess  required  one  to  one  and  one  half  days.  The  cream  was 
then  skimmed  off  with  a  shallow,  perforated  ladle.  One 
fifth  of  the  fat  was  left  behind  in  the  process.  This  made 
valuable  skimmed  milk,  but  cut  into  the  profits  of  butter- 
making.  The  milk  often  soured  and  suffered  other  de- 
compositions during  creaming  so  that  the  flavor  and  quality 
of  the  butter  were  injured. 

The  deep-setting  system  was  developed  about  the  year 
1885.  It  was  commonly  known  as  the  Cooley  creamery 
system.  In  this  system  the  milk  is  cooled  quickly  in  deep 
cans  by  placing  in  ice  water.  Creaming  goes  on  much  more' 
rapidly  than  in  the  shallow-setting  method  just  described. 
It  is  nearly  complete  in  about  twelve  hours,  when  the  skim 
milk  can  be  drawn  away  from  the  cream.  Only  one  tenth 
to  one  twentieth  of  the  total  fat  is  left  in  the  skimmed  milk. 
The  latter  remains  sweet  and  valuable  for  feeding.  The  best 
reason  given  for  the  more  rapid  rise  of  cream  in  the  deep- 
setting  method  than  in  the  shallow-setting  method  is  that 
chilling  prevents  the  formation  of  fibrin  threads.  It  is 
believed  that  in  the  warm  milk  fibrin  threads  form  which 
entangle  the  fat  globules  and  hinder  their  rise. 

Relation  of  Fat  Globules  to  the  Rate  of  Creaming.  If 
you  have  an  opportunity,  you  will  find  it  interesting  to 
compare  the  rate  at  which  cream  forms  on  the  milk  of  Jersey 
and  of  Holstein*  cows.  Place  the  two  milks  in  tall  glass  jars 
side  by  side.  The  reason  for  the  more  rapid  rise  in  the 
milk  of  Jersey  cows  is  that  its  fat  globules  are  larger  than 
those  of  the  other  milk.  Now,  as  your  study  of  geometry 
will  teach  you,  when  the  size  of  a  sphere  is  increased,  its 
surface  increases  much  less  rapidly  than  its  volume.  There 
is  less  surface,  therefore,  in  proportion  to  size  in  the  fat 
globules  of  milk  of  Jersey  cows  than  in  those  of  Holstein 
cows.  This  smaller  surface  offers  less  resistance  to  the  milk 
as  the  buoyancy  of  the  globules  tends  to  raise  them  to  the 
surface.    Hence  the  larger  globules  cream  more  quickly. 

20— 


306 


CHEMISTRY  OF  THE  FARM  AND  HOME 


CENTER  BAUHSED  BOWt 


The  centrifugal  method  has  now  almost  wholly  replaced 
the  setting  or  gravity  methods  of  creaming.  In  this  method 
the  milk  is  warmed  and  whirled  in  a  heavy  bowl  rotating 
several  thousand  times  per  minute.  This  treatment  acts 
like  the  whirling  of  a  sling.  The  heaviest  parts  go  to  the 
outside  and  the  hghter  parts,  like  leaves  in  a  whirlpool, 
go  to  the  center.     This  machine  used  for  the  centrifugal 

method  is  called  a 
cream  separator. 
In  its  rapidly  turn- 
ing bowl  the  heav- 
ier skimmed  milk 
is  thrown  toward 
the  rim  while  the 
lighter  cream  gath- 
ers at  the  center. 
The  two  then  run 
off  by  separate 
^^^^^^^^-"^SXr^^^^  spouts.  It  is  possi- 
ble to  regulate  the 
flow  of  cream  to 
thick  or  thin.  Thin 
cream  contains 
from  10  to  about 
30  per  cent  of  fat, 
while  thick  cream 
contains  30  to  50 
per  cent.  Thereiis 
n  o  advantage  in 
making  the  richest  cream.  In  fact,  cream  containing  25 
to  30  per  cent  of  fat  is  best  for  churning  and  other  purposes. 
The  separator  is  very  efficient.  Only  two  or  three  one  hund- 
redths of  the  total  fat  is  left  in  the  skimmed  milk.  When 
the  cream  is  made  in  any  of  the  ways  already  described 
it  contains  small   amounts   of   sugar,    proteins  and  salts 


Figure  93.     A  cream  separator.     It  separates  the 

heavier  constituents  of  milk  from  the  fat  by 

centrifugal  force.     Cream  rises  from  the  center 

of  the  bowl;  skimrailk,  from  its  circumference. 

— Courtesy  of  the  De  Laval  Separator  Co. 


DAIRY  PRODUCTS  307 

removed  from  the  milk.  The  sugar  and  proteins  undergo 
useful  chemical  changes  in  the  process  of  cream  ripening. 

Butter  is  made  by  agitating  cream  very  thoroughly. 
This  causes  the  separate  globules  to  fuse  gradually  into  small 
masses.  The  process  goes  on  best  at  temperatures  from 
50°  to  60°F.  This  is  brought  about  only  with  great  diffi- 
culty in  fresh  cream.  For  proper  churning  to  butter  the 
cream  must  be  soured.  It  was  once  the  custom  to  leave 
the  cream  in  a  moderately  warm  place  until  the  lactic  acid 
bacteria  finally  produced  the  necessary  amount  of  lactic 
acid  and  ripeness.  Along  with  this  desirable  change  other 
fermentations  unfavorable  to  the  flavor  of  the  butter  some- 
times occurred.  It  was  not  possible  to  maintain  that  uni- 
formity of  quality  so  desirable  in  the  marketed  product. 
It  is  now  general  practice  to  pasteurize  the  cream,  and  then 
add  starter.  Pasteurizing  or  heating  at  about  160°F.  kills 
nearly  all  bacteria.  The  starter  is  a  pure  culture  of  lactic 
acid  bacteria,  which  act  very  rapidly  in  the  pasteurized 
cream.  In  this  ripening  process  there  are  slight  decompo- 
sition changes  of  the  fat  and  protein  which  contribute  to 
the   flavor   of  the   butter. 

Churning  should  cease  while  the  butter  fat  is  still  in  a 
granular  condition.  It  can  then  be  treated  thoroughly  in 
the  washing  process.  This  is  the  process  in  which  the 
remaining  fluid,  or  buttermilk,  is  washed  away  from  the 
fat.  It  should  be  thorough,  so  that  harmful  decomposition 
changes  may  not  continue  in  the  butter.  Next,  salt  is 
worked  into  the  butter  to  impart  a  desirable  flavor.  If 
this  salt  and  the  water  which  remains  in  the  butter  are  not 
thoroughly  mixed  with  the  fat,  an  undesirable,  mottled 
appearance  is  likely  to  develop. 

Rancidity.  Exposure  of  butter  to  the  air  and  light  for 
a  long  time  develops  a  sharp  smell  and  taste.  The  butter 
is  said  to  become  rancid.  This  is  due  to  the  setting  free 
of  small  amounts  of  volatile  fatty  acids.     Rancid  butter 


308      CHEMISTRY  OF  THE  FARM  AND  HOME 

is  improved  by  melting  it  and  forcing  air  through  it.  It 
is  then  churned  with  sweet  milk.  The  product  is  marketed 
as   "renovated"   or  "process"   butter. 

Oleomargarine  is  a  butter  substitute  manufactured  from 
beef  fat  or  tallow.  The  liquid  fats  are  pressed  from  the 
solid  fats  at  summer  heat  and  then  churned  with  various 
other  fats.  The  product  is  salted  and  worked  like  butter. 
It  is  sometimes  called  butterine.  When  colored  in  imitation 
of  butter  a  tax  of  10c.  a  pound  is  charged  on  this  product 
by  the  United  States  government.  Uncolored  oleomar- 
garine is  taxed   3^  cent  a  pound. 

Overrun.  In  making  butter  from  milk  there  is  a  gain 
of  water,  salt  and  casein  of  about  one  sixth  of  a  pound  for 
each  pound  of  fat  in  the  milk.  In  other  words,  one  pound 
of  butter-fat  should  make  one  and  one  sixth  pounds  of  butter. 
The  amount  of  salt  added  is  about  one  ounce  per  pound  of 
butter.  The  water  generally  amounts  to  10  to  12  per  cent 
of  the  butter.  It  can  be  made  nearly  twice  as  great  and 
sometimes  is  fraudulently  made  so.  By  national  law, 
however,  it  is  limited  to  16  per  cent.  The  increased  weight 
of  butter  over  the  butter  fat  is  called  "overrun." 

Buttermilk  has  considerable  food  value.  By  heating  it 
for  about  two  hours  at  76°F.  and  then  raising  the  temp- 
erature to  140°F.  the  casein  and  albumin  can  be  caused 
to  separate  in  granules.  This  product  is  salted  and  pressed 
to  form  buttermilk  cheese. 

Cheese  is  commonly  made  from  milk  by  the  action  of 
rennet  extract.  This  extract  is  prepared  by  soaking  the 
fourth  stomach  of  young  calves  in  salt  solution.  The  milk 
is  ripened  until  0.2  or  0.3  per  cent  of. acid,  calculated  as 
lactic  acid,  is  present.  This  process  is  hastened  by  using 
a  starter  composed  of  sour  milk  or  a  culture  of  lactic  acid 
bacteria.  The  milk  is  then  warmed  to  about  83°F.  and 
rennet  added.  This  causes  the  casein  to  coagulate  and 
form  a  curd  by  the  action  of  the  enzyme  rennin.     Most  of 


DAIRY  PRODUCTS 


309 


the  fat  is  entangled  and  held  by  the  curd.  Afterwards  the 
firm  curd  is  cut  into  cubes  by  a  special  knife  with  several 
parallel  blades.  Then  it  is  heated  to  100°F.  This  is  about 
the  best  temperature  for  the  action  of  rennin.  At  low 
temperature  it  acts  slowly  and  at  130°F.  its  power  is  des- 
troyed.    By  keeping  the  cheese  vat  at  100°F.  for  one  to 

two  hours  the  curd 
shrinks.  The  whey  is 
then  drawn  off  and  the 
curd  pulls  together.  Fin- 
ally, it  is  ground,  salted 
and  pressed  in  molds. 
It  is  then  ''cured"  at 
temperatures  somewhat 
lower  than  those  of  liv- 
ing rooms.  Here  bac- 
teria and  molds  produce 
various  changes.  By  the 
decomposition  of  the 
casein  and  fat  com- 
pounds are  produced 
which  give  flavor  to  the 
cheese.  Gases  which  are 
set  free  also  give  por- 
osity and  texture  to  the 
product.  Cheese  made 
from  ill  kept  milk  often 
contains  bacteria  which  produce  too  great  porosity  of  the 
cheese  and  render  it  unmarketable.  Molds  are  impor- 
tant in  the  development  of  those  peculiar  flavors  so  much 
liked  in  Roquefort  and  other  soft  cheeses.  The  chemical 
changes  of  cheese  ripening  result  in  the  disappearance  of 
lactose  and  the  conversion  of  one  third  or  more  of  the 
proteins  to  soluble  compounds.  The  fat  also  partly  breaks 
down  and  fatty  acids  are  set  free.      Among  the  products 


igure 

The  cheese  at  the  top  was  made  from  clean 
milk.  That  at  the  bottom  was  made  from 
dirty  milk. 


310 


CHEMISTRY  OF   THE  FARM  AND  HOME 


of  these  changes  are  esters,  of  which  you  will  learn  in 
studying  human  foods.  These  compounds  are  important 
in  producing  flavors. 

COMPOSITION  OF  DAIRY  PRODUCTS. 

In  Table  XI  are  given  the  average  composition  of  butter 
and  cheese  and  their  by-products. 

Table  XI — The  Average  Composition  of  Some  Dairy  Products 


Ash 

% 


Butter 

Buttermilk 

Cheddar  cheese . 
Whey 


Water 
% 

Fat 

% 

Protein 
% 

Sugar  or 

lactic   acid, 

etc. 

% 

0.0 

11.5 

83.0 

2.1 

91.0 

0.5 

3.5 

4.3 

34.5 

32.5 

26.5 

3.0 

93.3 

0.3 

0.9 

4.9 

3.4 
0.7 
3.5 
0.6 


Babcock  and  Hart  Tests.     This  table  shows  the  great 
importance  of  fat  in  butter-making  and  of  fat  and  protein 
in  cheese-making.     It  is  very  important,  you  see  then,  to 
be  able  to  determine  these  consti- 
tuents quickly  in  milk.     They  are 
the  substances  to  be  paid  for  in  pur- 
chasing the  milk.      The   standard 
chemical  methods  for   determining 
these  constituents  require  consider- 
able time.     On  this  account  there 
have  been  developed  rapid  mechan- 
^  ^  ical    methods    for    separating    and 

J^^  'I  measuring   them.      These   are   the 

B^^H  I        '    well  known   Babcock  fat  test  and 

I^^H  the  newer  casein  test  developed  by 

—^^^H •  •""    Professor  Hart  of  the  Wisconsin  Ex- 

^m^  periment  Station.     Figure  95  shows 

the  appearance  of  the  completed 
tests.  In  the  Babcock  test  the 
casein  is  dissolved  by  strong  sul- 


Figure  95.  Finished  Babcock 
test  for  fat  (left)  and  Hart 
test  for  casein  (right). 


DAIRY  PRODUCTS  311 

phuric  acid.  The  liquid  fat  is  then  separated  by  centrifugal 
force  in  a  warmed,  rapidly  rotating  machine.  In  the  Hart 
test  the  fat  is  dissolved  by  chloroform.  The  casein  is  then 
coagulated  by  weak  acetic  acid  and  separated  in  a  com- 
pact column  by  a  centrifugal  force  of  definite  strength. 
These  tests  are  of  much  value,  as  they  can  be  rapidly  per- 
formed at  the  creamery  or  cheese  factory. 

Butter  and  Cheese  Flavors.  In  grading  or  scoring  butter 
and  cheese  upon  the  market  nearly  one  half  of  the  weight 
of  the  scorer's  rating  is  thrown  upon  the  single  quality  of 
flavor.  This  is  a  quality  in  the  measurement  of  which 
chemistry  is  as  yet  of  little  service.  Good  and  poor  cheeses 
or  butters  may  give  the  same  results  to  ordinary  chemical 
analysis.  The  flavoring  constituents  of  these  dairy  products 
are  present  in  so  small  amounts  as  to  baffle  for  a  long  time 
attempts  to  determine  them  in  a  chemical  way.  Like  musk 
and  the  odorous  compounds  of  many  flowers,  they  may  be 
so  powerful  in  their  action  upon  the  nerves  of  taste  and 
smell  that  mere  traces  determine  the  quality  of  the  butter 
or  cheese. 

SUMMARY 

The  development  of  dairying  is  widening  rapidly.  Its  products 
are  of  great  total  value.  These  conditions  make  it  especially  important 
for  the  dairyman  to  put  upon  the  market  products  uniformly  of  high 
quality.  To  attain  this  end  he  must  know  the  chemical  principles 
with  which  he  deals  and  the  influence  of  different  conditions  upon  them. 

Milk  is  secreted  from  blood  by  special  cells  of  the  body.  It  con- 
sists largely  of  water  in  which  are  dissolved  a  sugar  called  lactose, 
proteins  and  salts.  A  protein  called  casein  is  distributed  through  it 
in  the  finely  divided  form  of  colloidal  solution.  A  mixture  of  fats  is 
suspended  in  it  in  minute  droplets  which  form  as  emulsion.  The  phos- 
phates of  potassium  and  calcium  and  sodium  chloride  are  the  chief 
salts  present. 

Fat  varies  much  more  in  amount  than  any  of  the  other  compounds 
of  milk.  Some  breeds  of  cows,  such  as  Jerseys,  produce  milk  especially 
rich  in  fat.  The  amount  of  fat  in  milk  can  be  increased,  but  only  tem- 
porarily, by  increasing  the  fat  in  the  rations  fed.    The  composition  of 


312  CHEMISTRY  OF   THE  FARM  AND  HOME 

the  milk  fat  can  be  permanently  affected  by  the  kind  of  fat  in  the  feed- 
ing stuff.     In  this  way  hard  and  soft  butters  are  produced. 

Considerable  carbon  dioxide  is  present  in  freshly  drawn  milk. 
It  escapes  rapidly  and  is  replaced  by  the  gases  of  the  air  and  such 
odorous  substances  as  may  be  present.  This  necessitates  guarding 
the  milk  from  absorbing  undesirable  odors. 

Milk  is  very  prone  to  decomposition  by  bacteria,  chief  of  which 
are  those  producing  lactic  acid  from  lactose.  Cooling  the  milk  checks 
these  bacteria  and  pasteurizing  kills  them.  Condensed  milk  and  milk 
powder  are  forms  to  which  milk  is  converted  for  improving  its  keeping 
qualities  and  cheapening  cartage.  The  use  of  chemical  preservatives, 
which  both  encourage  unsanitary  conditions  in  the  dairy  and  endanger 
the  health  of  the  pubhc,  should  be  prohibited. 

Cream  consists  of  the  milk  fat  as  separated  by  gravity  or  the  cream 
separator,  together  with  water  and  other  milk  compounds.  Large 
fat  globules  cream  more  readily  than  small  ones.  The  separator  is 
much  more  efficient  than  gravity  in  creaming. 

Butter,  the  gathered  fat  from  cream,  requires  for  its  preparation 
attention  to  the  ripeness,  or  sourness,  of  the  cream  and  its  temperature. 
It  must  be  thoroughly  washed  and  worked  to  insure  good  keeping 
quality  and  uniform  texture  and  appearance.  Rancidity,  or  sourness, 
develops  in  butter  by  excessive  exposure  to  air  and  light.  Oleomar- 
garine is  a  butter  substitute  made  from  the  softer  parts  of  tallow. 

Cheese  consists  of  the  curdled  casein  of  milk  and  fat  and  other 
compounds  removed  with  it.  As  it  ripens  the  compounds  become  more 
soluble  and  partly  disappear.  Gases  which  are  produced  give  it  a 
porous  texture.     Other  compounds  produced  give  various  prized  flavors. 

The  Babcock  fat  test  and  Hart  casein  test  provide  means  for 
quickly  determining  the  value  of  milk  for  butter  and  cheese  making. 
The  ingredients  of  these  dairy  products  which  produce  that  most  im- 
portant quality  termed  flavor  have  so  far  pretty  much  escaped  the  grasp 
of  the  analytical  chemist. 

QUESTIONS 

1.  From^what  body  fluid  is  milk  produced? 

2.  For  what  purpose  is  the  lactometer  used? 

3.  Why  is  milk  heavier  than  water? 

4.  What  per  cent  of  solid  matter  does  whole  milk  contain? 

5.  What  is  lactose? 

6.  Which   constituent  of  milk  solids  varies  most  in   amount? 

7.  How  does  milk  fat  differ  from  the  fat  of  oleomargarine  in 
composition? 

8.  What  is  the  chief  protein  of  milk? 

9.  Name  three  bases  and  two  acids  abundant  in  milk  ash. 


DAIRY  PRODUCTS  313 

10.  What  two  constituents  of  woman's  milk  are  deficient  as 
compared  with  cow's  milk? 

11.  What  are  the  two  factors  chiefly  influencing  the  compostion 
of  cow's  milk? 

12.  How  do  feeding  stuffs  aflFect  the  melting  point  of  butter-fat? 

13.  Why  should  milk  be  removed  from  the  stable  as  soon  as 
drawn? 

14.  What  causes  the  souring  of  milk? 

15.  Why  is  the  use  of  preservatives  objectionable? 

16.  How  are  condensed  milk  and  milk  powder  prepared? 

17.  Why  does  the  milk  of  Jersey  cows  cream  more  rapidly  than 
that  of  Holsteins? 

18.  How  is  the  improvement  of  creaming  by  cooling  the  milk 
explained? 

19.  Upon  what  principle  is  the  cream  separator  based? 

20.  What  is  the  action  of  the  churn  in  butter-making? 

21.  What  chief  advantage  is  secured  by  pasteurizing  the  cream 
and  using  starter  before  churning? 

22.  Why  is  thorough  working  of  the  butter  important? 

23.  What  is  the  cause  of  rancid  butter? 

24.  What  is  the  overrun? 

25.  To  what  value  is  it  limited  by  law? 

26.  What  is  rennin? 

27.  What  chemical  changes  occur  in  the  curing  of  cheese? 

28.  What  is  the  service  of  the  Babcock  test  to  the  dairy  industry? 
The  Hart  test? 

29.  Can  quality  of  cheese  or  butter  be  measured  chemically? 


CHAPTER  XIII 
HUMAN  FOOD  AND  DIETETICS 

Man's  Dietetic  Needs.  Food  includes  all  substances 
whose  compounds  either  supply  energy  to  the  animal  body 
or  promote  growth,  or  do  both,  without  harmful  effect.  One 
might  consider  scientific  feeding  to  be  the  same  for  human 
beings  as  for  farm  animals.  They  are  closely  akin.  The 
processes  of  digestion  are  essentially  the  same  in  man  and 
live  stock.  By  a  little  study  you  will  be  able  to  make  quite 
a  list  of  foods  which  the  two  eat  in  common.  On  the  other 
hand,  we  can  find  differences  which  give  to  the  feeding  of 
man  great  importance  as  a  special  subject  for  study. 

Dietetics  presents  the  kinds  and  forms  of  food  with  the 
principles  governing  their  use. 

In  order  to  make  the  importance  of  this  subject  clearer, 
let  us  try  to  answer  the  following  questions: 

First:  How  are  human  foods,  in  contrast  to  animal 
foods,  generally  treated  before  serving?  Is  this  treatment 
likely  to  have  any  effect  upon  the  composition  and  digesti- 
bility of  food  stuffs? 

Second:  Which  has  the  more  varied  activities,  man  or 
the  common  animals?  Will  these  differences  of  activity 
require  any  differences  of  attention  to  food  values? 

Third:  Has  man  or  the  common  animals  the  more 
cultivated  sense  of  taste?  What  special  factor  in  the  prepa- 
ration of  meals  is  magnified  by  this  difference? 

Is  it  not  now  clear  that  dietetics,  or  the  scientific  bal- 
ancing of  human  food  rations,  requires  even  more  frequent 
and  closer  attention  than  the  feeding  of  animals? 

The  practice  of  dietetics  requires  a  knowledge  of  the 
composition  and  fuel  value,  or  energy-supplying  power,  of 

314 


HUMAN  FOOD  AND  DIETETICS  315 

foods.  We  shall  take  up  these  subjects  in  succeeding  par- 
agraphs. The  several  organic  compounds  which  will  need 
consideration  have  become  familiar  already  in  our  study  of 
''The  Plant  and  Its  Products."  We  have  previously  also 
learned  about  the  processes  of  digestion,  nutritive  ratio 
and  fuel  value  of  foods  in  our  study  of  ''The  Animal  and 
Its  Products."  Hence  it  is  unnecessary  to  consider  these 
topics  at  this  place. 

Fuel  Needs  of  the  Human  Body.  The  methods  of 
measuring  the  food  requirements  of  man  and  the  efficiency 
of  his  foods  have  been  highly  developed.  Figure  81  shows 
the  respiration  chamber  or  calorimeter  and  its  accessory 
apparatus  with  which  such  studies  have  been  conducted 
with  cattle.  By  similar  nutrition  experiments  it  has  been 
found  that  the  fuel  requirements  of  a  middle-aged  man  of 
average  size,  or  of  150  pounds  weight,  is  about  65  calories 
an  hour  when  he  is  asleep.  This  is  equal  to  the  heat 
produced  by  the  complete  burning  of  16  grams  of  sucrose. 
If  you  calculate  this  value  in  avoirdupois  units,  you  will 
find  it  to  be  a  moderate  quantity.  Would  you  expect  the 
fuel  requirements  to  be  changed  much  by  awaking,  but 
remaining  at  rest?  The  fuel  value  of  the  food  necessary 
for  this  state  is  called  the  maintenance  requirement.  It 
will  be  well  to  write  a  definition  for  it  in  your  own  words. 
Strange  to  say,  this  requirement  amounts  to  about  100  cal- 
ories, or  much  more  than  the  sleep  requirement.  The 
energy  requirement  of  man  is  put  to  several  uses,  roughly 
as  follows: 

Digestion  processes 10  per  cent 

Circulation  of  blood 8  per  cent 

Respiration 15  per  cent 

Muscular  tension  or  "tone" 40  per  cent 

Other  purposes 27  per  cent 

Note  which  of  these  factors  consumes  the  most  fuel 
value.  It  is  to  this  that  the  increased  requirement  of  wake- 
ful over  sleeping  hours  is  due.     The  distribution  of  the  fuel 


316      CHEMISTRY  OF  THE  FARM  AND  HOME 

value  of  food  for  producing  the  energy  required  by  the 
organs  suggests  somewhat  the  principle  of  the  steam  engine. 
How  would  you  expect  work  to  affect  the  fuel  requirement? 
A  man  actively  working  needs  about  290  calories  and  at 
very  severe  labor  he  needs  600  calories  per  hour.  Is  not 
this  comparison  sufficient  to  show  the  great  importance  of 
the  fuel  value  of  foods?  Dividing  the  preceding  fuel  needs 
proportionately  among  the  various  ways  a  man  lives,  his 
total  need  for  a  day  is  about  3,800  calories.  This  value 
must  be  kept  in  mind  in  balancing  foods  for  the  table. 

While  the  temperament  of  the  individual,  especially 
his  muscular  tension,  varies  greatly,  woman  requires  gener- 
ally about  0.8  as  many  calories  as  man.  In  addition  to 
muscular  activity,  one  must  take  into  account  the  need  of 
maintaining  a  constant  body  temperature  of  about  98°  F. 
These  two  factors  make  the  fuel  requirement  of  children 
comparatively  high.  Besides  their  characteristic  muscular 
activity  they  have  more  surface  in  proportion  to  weight 
than  adults.  They  are,  therefore,  more  subject  to  loss  of 
body  heat  in  cold  weather.  Children  less  than  two  years 
of  age  require  0.3  as  many  calories  as  adults.  Their  need 
increases  by  0.1  the  full  need  of  man  with  about  each  three 
successive  years  of  age.  For  equal  weight  of  body  the  child 
of  two  years  of  age  or  under  requires  twice  as  much  fuel 
value  in  its  food  as  the  adult.  Is  not  this  sufficient  reason 
for  the  prodigious  appetite  of  the  average  small  boy?  It 
is  but  a  normal  demand  which  must  be  properly  satisfied. 

Protein  Needs  of  the  Human  Body.  It  was  once  thought 
that  work  destroyed  the  protein  compounds  of  the  muscle 
and  that  this  change  was  the  source  of  energy  for  work. 
Now,  however,  we  know  that  this  energy  is  derived  from 
the  burning  of  sugar  in  the  muscle  cells.  This  process 
results  in  greater  excretion  of  water  and  carbon  dioxide, 
instead  of  such  waste  nitrogen  compounds  as  would  result 
from  protein.      So  one  breathes  and  perspires  more  at  work 


HUMAN  FOOD  AND  DIETETICS 


317 


than  at  rest.  Protein  can  furnish  energy  equal  to  that  pro- 
duced by  sugar,  and  in  case  of  starvation  the  proteins  of 
the  muscles  do  so.  Its  use  in  this  manner  is  wasteful,  how- 
ever. Carbohydrates  and  fat,  the  latter  2.4  times  as  efficient 
as  the  former,  are  the  true  fuel  compounds  of  foods.  Pro- 
tein owes  its  great  value  to  its  importance  in  growth  and 
repair  of  the  body.  If  you  will  review  the  composition 
and  work  of  protoplasm,  as  given  under  "The  Plant  and 
Its  Products,"  you  will  see  good  reasons  for  this  importance. 
Protein  is  wasted  by  feeding  too  much  fat,  as  well  as  by 
feeding  too  little.  In  the  former  case,  the  protein  of  the 
body  seems  to  be  overtaxed  to  digest  and  assimilate  the  fat. 
In  the  latter  case,  the  food  or  body  protein  is  used  to  fill 
the  lack,  if  carbohydrates  are  also  lacking. 

The  requirement  of  protein  for  the  repair  and  growth 
of  the  tissues  of  the  body  is  as  important  as  the  fuel  require- 
ment just  described.  The  amount  of  protein  in  the  food 
necessary  to  meet  the  daily  needs  of  the  average  man  has 
been  placed  at  60  grams.  With  this  amount  most  persons 
neither  lose  nor  gain  protein  of  the  body.  To  merely  bal- 
ance the  protein  is  not  enough,  however.  Most  scientists 
agree  that  double  the  preceding  amount  should  be  supplied, 
on  account  of  some  special  stimulating  effects  for  which  the 
body  needs  a  liberal  supply  of  this  food  constituent. 

Working  Men's  Needs.  The  food  requirements  of  men 
at  light  and  heavy  labor  as  provided  for  in  different  countries 
is  interesting,  as  given  in  the  following  figures: 

Table  XII — Human  Food  Standards  for  Different  Countries 


Occupation 


Business  men  and  students . 
Laboring  men 


Grams    of 

Country 

Protein 

per  day 

United  States 

106 

France 

110 

United  States 

100 

England 

89 

Germany 

134 

Japan 

118 

Calories  of 

fuel  value 

per  day 

3,285 
2,750 
3,425 
2,685 
3,061 
4,415 


318 


CHEMISTRY  OF  THE  FARM  AND  HOME 


The  average  of  many  statistics  of  this  sort  shows  that 
"the  world  over"  a  man  receives  daily  about  100  grams  of 
protein  and  3,000  calories.  These  values  are  somewhat 
lower  than  high  authorities  recommend. 

Classes  of  Food  Stuffs.    We  can  now  consider  the  several 

classes  of  food  stuffs  in  the  light  of  man's  food  requirements. 

For  the  sake  of  convenience,  let  us  classify  foods  into  two 

groups,  as  follows: — 

Energy  supplying  foods: 
Cereal  grain  products 


Protein  supplying  foods: 
Meat  and  fish 


Milk  and  eggs 
Legume  vegetables 


Vegetables 

Nuts 

Fruits 


Table  XIII — Food  Values  of  Some  Important  Food  Stuffs  as  Purchased 


Animal  Foods 
Beef,  sirloin  steak . 
Mutton,  chops. . .  . 
Pork,  smoked  ham 

Poultry,  fowl 

Fish,  dressed  cod . . 

Eggs,  of  hens 

Milk,  whole 

Vegetable  Foods 

Bread,  white 

Oat  meal 

Beans,  dried 

Peas,  shelled 

Potatoes 

Tomatoes 

Apples 

Bananas 

Hickory  nuts 

Peanuts 

Cocoa,  powered . .  . 


Nutrienta 

Water 
per 
cent 

Protein 

Fat 

Carbohy- 
drates 

per  cent 

per  cent 

per  cent 

54.0 

16.5 

16.1 

42.0 

13.5 

28.3 

34.8 

14.2 

33.4 

47.1 

13.7 

12.3 

58.5 

11.1 

0.2 

65.5 

13.1 

9.3 

87.0 

3.3 

4.0 

5.0 

35.3 

9.2 

1.3 

53.1 

7.7 

16.7 

7.3 

66.2 

12.6 

22.5 

1.8 

59.6 

74.6 

7.0 

0.5 

16.9 

62.6 

1.8 

0.1 

14.7 

94.3 

63.3 

48.9 

1.4 

6.9 

4.6 

0.9 
0.3 
0.8 
5.8 
19.5 
21.6 

0.4 

0.3 

0.4 

25.5 

29.1 

28.9 

3.9 
10.8 
14.3 

4.3 
18.5 
37.7 

Fuel  Value 


Calories 
per  pound 


975 
1,415 
1,635 
765 
220 
635 
310 


1,200 

1,800 

1,520 

440 

295 

100 

190 

260 

1,145 

1,775 

2,160 


Table  XIII  gives  the  food  values  of  some  important  food 
stuffs.     For  more  complete  tables  one  must  refer  to  special 


HUMAN  FOOD  AND  DIETETICS 


319 


texts.  Is  water  a  nutrient  compound  in  foods?  Suppose 
all  the  water  were  removed  from  these  materials.  How 
would  that  affect  the  present  difference  of  value  per  pound 
between  oatmeal  and  potatoes,  for  example? 

Meats,  Milk,  Eggs.  The  preceding  table  shows  that, 
with  the  exception  of  milk,  the  animal  foods  do  not  contain 
appreciable  amounts  of  carbohydrates.  With  the  exception 
of  eggs  and  fish,  the  animal  foods  supply  as  much,  or  more, 
fat  as  protein  and  rank  well  in  fuel  value.  Fish,  however, 
forms  practically  a  protein  food.  It  is  well  balanced  by 
the  Japanese  against  the  high  fuel  value  of  rice. 

Vegetables.    Among  the  vegetables,  beans  and  the  other 

legume  seeds  are  distinct- 
ively rich  in  protein,  yet 
these  contain  enough 
carbohydrates  to  form  a 
large  part  of  the  fuel 
required  by  their  protein 
for  a  balanced  food  ra- 
tion. Bread  and  the 
other  cereal  grain  prod- 
ucts are  distinctly  fuel 
foods,  due  to  their  high 
content  of  starch.  The 
very  watery  fresh  vege- 
tables and  fruits  have 
little  direct  food  value. 
Besides,  on  account  of 
the  protecting  action  of 
their  cellulose  com- 
pounds, the  digestive 
secretions  act  less  thor- 
oughly upon  them  than  upon  other  foods.  Their  value 
lies  chiefly  in  either  laxative  or  flavoring  effects.  Some 
nuts    have    the  highest  value  of  all  food  stuffs,  because 


Figure  96.  Wheat  and  its  food  products.  The 
second  cylinder  contains  the  amount  of 
bran  and  gluten  layers  present  in  the 
wheat  grain  of  the  first  cylinder.  The 
third  cylinder  contains  the  amount  of  germ 
or  embryo  this  wheat  would  yield.  The 
last  cylinder  contains  the  amount  of  starch 
cells  present  in  the  wheat  of  the  first  cylin- 
der. In  milling  good,  hard  wheat  about 
70  per  cent  of  the  grain  is  turned  out  as 
flour,  13  per  cent  as  bran,  6  per  cent  as 
middlings  and  6  per  cent  as  "red  dog"  and 
Bcreenings.  The  latter  by-products  are 
familiar  cattle  feeds.  They  contain  coat- 
ing and  germ  cells,  with  some  starch. 


320 


CHEMISTRY  OF  THE  FARM  AND  HOME 


nearly  all  contain  much  fat,  besides  considerable  pro- 
tein. The  peanut  is  especially  rich  in  these  compounds. 
Such  food  stuffs,  however,  are  too  ' 'heavy' ^  to  be  con- 
sumed in  great  quantity.  Hence,  they  must  form  a 
small,  supplementary  part  of  meals.  Cocoa  differs  from 
other  common  beverage-forming  substances  by  its  high 
food  value.  You  will  find  it  helpful  now  to  secure  larger 
tables  of  food  values  and  make  lists  of  foods  rich  in  protein 
and  those  high  in  fuel  value. 

Cereal  Grains.  On  account  of  the  enormous  quantity 
of  human  foods  supplied  by  the  milling  of  wheat  and  other 
cereals,  these  grains  deserve  special  study.  The  ''bumper" 
crop  of  wheat  in  our  country  for  1914  was  estimated  as  nine 
billion  bushels,  and  this  was  but  one  fourth  of  the  world's 
crop.  In  the  milling  process  most  of  the  starch  of  this 
grain,  which  forms  85  per  cent  of  it,  goes  to  produce  flour. 
The  flour,  therefore,  contains  about  3  per  cent  more  starch 
and  2  per  cent  less  protein  than  the  whole  grain.  About 
half  of  the  fat  and  ash  constituents  are  lost  in  the  germ  and 
bran,  and  about  80  per  cent  of  the  phosphorus  of  the  grain 
is  contained  in  the  bran.  This  fact  has  led  to  the  belief 
that  white  bread 
supplies  insuffi- 
cient phosphor- 
us for  man.  This 
theory  does  not 
seem  to  be  true 
for  adults  on 
mixed  diet;  but 
it  should  be  care- 
fully considered 
in  feeding  moth- 
ers and  growing 

children.        They       Figure  98.     Transplanting  rice  in  Japan.      This  inter- 
1  V       1-  esting  crop  provides  the  chief  food  of   more   than  half 

need  much  pnOS-  the  human  race.— By  courtesy  of  Mrs.  F.  H.  King. 


HUMAN  FOOD  AND  DIETETICS 


321 


phorus  for  the  production  of  milk  and  the  growth  of  bones. 
The  favorable  laxative  effects  of  whole  wheat  or  graham 
breads  probably  are  due  both  to  their  fibrous  nature  and  to 
their  phosphorus  compounds.  Bread,  macaroni  and  other 
flour  products  owe  their  making  to  the  gluten  of  the  grain. 
This  is  a  mixture  of  two  proteins.  One  of  them,  gliadin,  is 
soluble  in  strong  alcohol.  The  other  is  soluble  only  in 
alkali  solution.  In  good  bread-making  wheat  gluten  forms 
about  85  per  cent  of  all  the  protein.  Gliadin  should  form 
about  65  per  cent  of  the  gluten.  No  definite  percentage  of 
protein  has  been  found  to  insure  good  bread-making  qualities 
of  wheat.  It  is  certain,  however,  that  too  much  produces 
wet,  **soggy"  bread.  On  the  other  hand,  too  little  produces 
dry  bread  of  poor  quality.  Rye  contains  gluten  with  bread- 
making  properties  much  inferior  to  that  of  wheat.  None 
of  the  other  grains  possesses  this  valuable  constituent. 

Besides,  in  the  making  of  bread  and  pastry,  the  cereal 
grains,  as  barley,  are  used  for  soups.     You  are  familiar, 

too,  with  their  wide 
use  as  breakfast  food, 
either  raw  or  cooked. 
The  latter,  as  corn 
flakes,  are  prepared 
by  slicing  or  shredding 
and  toasting  the 
grains.  They  are  of 
nearly  the  same  com- 
position as  the  raw 
grain,  except  that  the 
heating  produces  sol- 
uble carbohydrates, 
as  dextrins  and 
sugars,  from  the  starch.  These  add  flavor  to  the  products. 
A  few,  as  grape  nuts,  contain  considerable  sugar  and  salt 
added  for  this  purpose.     There  is  no  appreciable  difference 

21— 


Figure  97.  The  relation  of  proteins  to  bread-mak- 
ing. The  loaf  on  the  left  waa  made  from  whole 
flour.  The  middle  loaf  was  made  from  flour 
which  lacked  gliadin.  The  right  hand  loaf  was 
made  from  flour  which  had  been  extracted  with 
water. 


322  CHEMISTRY  OF  THE  FARM  AND  HOME 

of  digestibility  between  these  products  and  the  home-cooked 
breakfast  foods. 

Fruits.  Besides  their  high  percentage  of  water,  fruits 
consist  mostly  of  sugars  and  acids  enclosed  in  the  cellulose 
compounds  which  form  the  pulp.  The  hardness  of  green 
fruits  is  due  to  pectose,  a  substance  of  carbohydrate  nature. 
Such  fruits  contain  considerable  starch  also.  As  they  ripen 
the  pectose  is  changed  to  pectin,  a  soluble  substance,  and 
the  starch  to  sucrose,  dextrose  and  levulose.  Thus  the  fruit 
mellows  and  acquires  flavor.  The  latter  is  due  chiefly  to 
the  kinds  and  amounts  of  organic  acids  and  to  traces  of 
essential  oils.  The  latter  are  neutral  bodies  resembling 
waxes  in  composition  and  of  pleasing  flavor  and  odor. 
Malic  acid,  the  most  common  acid  of  fruits,  forms  about 
1  per  cent  of  the  juice  of  sour  apples.  Tartaric  acid,  either 
free  or  as  acid  salts,  forms  1  to  5  per  cent  of  grape  juice  and 
citric  acid  forms  about  7  per  cent  of  lemon  juice.  The 
essential  oil  of  the  apple  is  ethyl  acetate,  a  compound  of 
common  alcohol  with  acetic  acid,  the  characteristic  acid  of 
vinegar.  This,  and  related  oils,  such  as  those  of  the  pine- 
apple and  banana,  can  be  prepared  readily  in  the  laboratory. 
On  account  of  the  small  amount  of  nutrients  they  contain, 
fruits  must  be  given  value  chiefly  for  their  laxative  effects 
and  the  stimulation  of  appetite. 

<-Q^   Q  Ciders,  wines  and  vinegars  derive 

Q  ^jCi        their  valued  properties  from  the  fermen- 

^feOD^  ^      ^      tation  of  sugars  in  the  fruit  j  uices.  When 

0     O    °  Q     the  juice  is  ''seeded"  with  certain  low 

fN      ^/?^^*io         forms  of  plant  life,  the  yeasts,  the  lat- 

^^  0    §        ter  act  upon  the  sugars  and  produce 

alcohol  and  carbon  dioxide.     Figure  99 

^'|"aSt%  s^n^Sr     shows  the  manner  in  which  yeast  grows 

N?w%lfi3°for''m^by     by  buddiug.      Since  these  plants  are 

oM  oS.^"  *''°°'  *^'     ever  present  in  the  air  and  on  fruits  the 


HUMAN  FOOD  AND  DIETETICS  323 

juices  "seed''  naturally  and  fermentation  proceeds  without 
attention.  After  this  process  has  been  completed,  another 
fungus  forms  acetic  acid  from  the  alcohol  and  produces 
vinegar.  This  fungus  occurs  in  gelatinous  masses  in  vin- 
egar barrels,  whence  its  common  name  ''mother  of  vin- 
egar." Only  2  or  3  per  cent  of  alcohol  accumulates  in 
apple  cider.  Cider  vinegar  must  contain  4  per  cent  or 
more  of  acetic  acid  to  meet  the  requirements  of  the  national 
food  laws. 

Cooking,  as  suggested  early  in  our  present  study,  may 
alter  the  composition  of  food  stuffs.  It  changes  the  physi- 
cal structure,  however,  much  more  than  the  chemical  com- 
position. What  change  have  you  observed  in  the  texture 
of  meat  and  vegetables  as  they  are  boiled?  There  are 
present  in  meat  juices  soluble  proteins,  carbohydrates  and 
salts.  These  form  only  a  small  part  of  the  whole  meat, 
however.  If  the  meat  is  boiled,  something  over  10  per 
cent  of  the  protein  and  80  per  cent  of  the  salts  are  extracted. 
These  give  value  to  the  broth.  It  was  formerly  believed  that 
plunging  the  meat  directly  into  hot  water  formed  a  sort  of 
crust  of  coagulated  protein  and  reduced  the  loss  of  food 
compounds  into  the  broth.  It  is  now  known  that  no  greater 
loss  occurs  when  the  meat  is  placed  in  cold  water  and  grad- 
ually raised  to  boiling.  By  dry  cooking,  as  roasting  or 
frying,  the  surface  tissues  are  quickly  closed.  Meat  cooked 
in  this  way  retains  about  one  half  the  soluble  compounds  of 
the  raw  flesh.  It  is  about  2.5  times  richer  in  these  compounds 
than  boiled  meat.  Any  sort  of  cooking  removes  much  of 
the  water  of  fresh  meat,  while  improving  its  texture  and 
flavor.  The  total  food  value  is  little  influenced,  however, 
by  any  method  of  cooking. 

In  the  cooking  of  eggs,  as  with  other  protein-rich  foods, 
there  is  but  a  slight  decrease  of  digestibility  of  the  protein 
compounds.  ''Hard  boihng"  reduces  the  digestibility  of 
the  white  of  egg;  probably  because  it  is  less  thoroughly 


324  CHEMISTRY  OF  THE  FARM  AND  HOME 

masticated  and  exposed  to  the  digestive  fluids  of  the  body 
than  is  a  ''soft  boiled"  egg.  The  pasteurization  of  milk  was 
at  one  time  believed  to  seriously  affect  its  food  value.  Care- 
ful study  has  shown,  however,  that  it  produces  no  appre- 
ciable changes  of  composition  or  digestibility. 

Baking.  The  baking  of  bread  and  pastry  includes  the 
common  process  of  lightening  the  dough  by  ''raising.'* 
.This  produces  the  light,  leavened  bread  so  much  superior 
to  the  heavy,  unleavened  material.  This  interesting  and 
important  process  is  produced  chiefly  by  releasing  carbon 
dioxide  within  the  mass  of  dough.  In  escaping,  this  expands 
the  dough  to  a  light,  porous  mass  which  "sets"  by  baking. 
In  bread-making,  yeast  is  added  to  produce  the  carbon 
dioxide.  From  your  previous  study  of  fermentation  what 
compounds  would  you  expect  it  to  act  upon?  Like  other 
low  organisms,  it  is  well  supplied  with  enzymes.  These 
convert  the  starch  of  the  dough  to  sugars,  and  the  latter 
to  alcohol  and  carbon  dioxide.  What  effect  do  you  remem- 
ber increase  of  temperature  to  have  upon  the  speed  of 
chemical  reactions?  To  a  limited  extent  enzyme  processes 
are  affected  in  the  same  manner.  So  we  find  the  rising  of 
dough  hastened  by  keeping  it  in  a  moderately  warm  place. 
Thirty  degrees  Centigrade  is  the  best  temperature.  How 
many  degrees  Fahrenheit  is  it  equivalent  to?  The  products 
formed  largely  escape  in  the  baking.  A  small  amount 
of  organic  acids,  chiefly  the  lactic  acid  characteristic  of 
sour  milk,  is  produced  in  the  fermentation.  This  gives 
acidity  and  flavor  to  the  dough  and  bread. 

In  other  flour  products  than  bread,  the  raising  of  the 
dough  is  generally  accompHshed  by  means  of  baking  pow- 
ders. These  substances  consist  of  mixtures  of  sodium 
acid  carbonate  with  acid  salts.  Cream  of  tg-rtar  contains 
potassium  acid  tartrate.  Phosphate  powder^  contain  cal- 
cium acid  phosphate.  Alum  powder  contains  potassium 
aluminium  sulphate,  one  of  the  alums,    and  sometimes 


HUMAN  FOOD  AND  DIETETICS 


325 


also  calcium  acid  phosphate.  What  well  known  gas  will 
be  released  when  these  powders  are  moistened,  and  how 
is  it  produced?  Alum  powder  is  objectionable  on  account 
of  the  irritating  effect  of  aluminium  salts  on  the  digestive 
organs.  A  good  baking  powder  will  release  at  least  10 
per  cent  of  its  weight  of  carbon  dioxide.  Do  you  see  why 
it  is  important  that  these  powders  be  kept  dry? 

Baking  removes  a  large  part  of  the  water  from  bread 

dough.  It  also 
volatilizes  some 
of  the  organic 
acids  and  most  of 
the  gaseous  pro- 
ducts of  ferment- 
ation already 
named.  Part  of 
the  starch  is 
changed  to  dex- 
trins,  sugars, 
and  traces  of 
give  flavor  and 
of   the    total 


Fgure  100.  The  effect  of  popping  on  the  corn  grain.  On 
the  left,  the  starch  granules  are  greatly  swelled.  On 
the  right,  they  have  burst  the  cell  walls  and  become 
nearly  as  large  as  the  original  cells  of  the  grain. 


gaseous    hydrocarbons.     These    products 
aroma  to   the   bread.     About    15   per   cent 
starch  of  the  flour  is  lost  in  this  manner. 

Toasting  of  bread  and  popping  of  corn  produce  chemical 
changes  like  those  just  attributed  to  baking.  Chief  among 
these  changes  is  the  loss  of  water,  as  shown  by  the  shrinkage 
and  increase  of  brittleness  in  the  food  stuffs.  The  explosive 
escape  of  steam  from  the  corn  ruptures  the  kernel  and 
disintegrates  its  cells.  The  dextrins,  hydrocarbons,  and 
other  products  formed  enhance  the  flavor  and  palatability 
of  these  foods. 

Cooking  of  Vegetables.  Vegetables  are  especially  val- 
uable when  eaten  raw,  as  cabbage,  lettuce,  and  tomato  in 
salads;  for  in  this  form  all  the  ash  constituents  are  obtained. 
The  former  two  and  spinach  have  nutritive  ratios  as  narrow 


326  CHEMISTRY  OF  THE  FARM  AND  HOME 

as  1 :4,  whereas  in  most  vegetableSj  the  ratio  is  twice  as  wide. 
Frequently,  however,  not  more  than  one  half  of  the  nitrogen 
compounds  of  these  foods  are  proteins.  In  the  usual  methods 
of  cooking  vegetables,  as  stewing,  or  boiling,  they  lose  one 
third  to  one  half  of  their  food  value  in  the  water.  Hence 
they  are  best  cooked  as  soups  or  stews.  Potatoes,  especially, 
often  lose  much  of  their  nutrients,  excepting  starch,  by 
soaking  for  a  long  time  in  cold  water,  when  peeled.  They 
should  be  baked  or  boiled  in  their  ^'jackets,"  if  the  most" 
value  is  to  be  obtained  from  them. 

Have  you  observed  how  quickly  some  vegetables,  espec- 
ially the  potato,  and  various  fruits  turn  black  upon  freshly 
cut  surfaces?  This  change  of  color  is  due  to  the  oxidation 
of  a  protein-related  compound  by  an  enzyme.  Changes 
of  composition  also  occur  in  whole  stored  vegetables,  fruit, 
and  grains.  They  are  such  as  we  have  found  to  occur  in 
silage-making.  At  high  temperatures,  as  at  30°  C,  res- 
piration is  rapid.  From  your  previous  study,  what  com- 
pounds do  you  think  support  this  respiration?  What 
products  are  formed?  As  they  disappear  the  starch  is 
drawn  upon  to  replace  them.  This  causes  the  tuber  to 
soften  and  lose  quality.  At  temperatures  approaching  freez- 
ing, on  the  other  hand,  respiration  is  checked,  but  sugar 
continues  to  accumulate  slowly  by  enzyme  action.  This 
excessive  respiration  at  high  temperature  decreases  the 
quality  of  the  tubers.  The  best  temperature  for  the  storage 
of  potatoes  is  about  8°C.  Considerable  study  has  been 
made  of  the  relations  between  cooking  qualities  and  chem- 
ical composition  of  potatoes.  It  has  been  found,  that  the 
factors  which  determine  quality  are  too  obscure  to  be  yet 
determined  by  chemical  analysis. 

Spices  and  flavoring  extracts  owe  their  characteristics 
in  large  part  to  essential  oils.  These  compounds  have 
been  described  already.  They  serve  chiefly  to  stimulate 
the  flow  of  digestive  secretions,  as  saliva  and  gastric  juice, 


HUMAN  FOOD  AND  DIETETICS 


327 


and  "whet"  the  appetite.  Do  you  think  the  amounts  of 
these  materials  used  appreciably  increase  the  protein  or 
fuel  value  of  the  food?  Some  are  derived  from  fruits,  as 
pepper,  mustard,  allspice,  and  nutmeg.  Cinnamon  is  a 
tree  bark  and  ginger  is  prepared  from  the  root  of  a  plant 
by  that  name.  Cloves  are  the  dried  flower  buds  of  a  trop- 
ical evergreen 
tree.  The  active 
substances  of 
pepper  are  a  vol- 
atile oil  and  5 
or  6  per  cent  of 
the  alkaloid  pip- 
erine.  Mustard 
owes  its  sharp 
taste  to  an  or- 
ganic sulphur 
compound,  a 
close  relative  of 
the  compound 
giving  character  to   onions   and   garlic. 

Beverages,  as  tea  and  coffee,  generally  are  drunk  in  so 
small  amounts  daily  as  to  be  of  little  importance  as  food. 
The  two  materials  named  have  stimulating  properties,  due 
to  an  alkaloid,  caffein,  which  acts  on  the  nerves  and  heart. 
With  most  adult  persons  the  effects  are  mild.  The  bitter 
taste  of  tea  is  due  to  tannin.  This  beverage  is  prepared 
from  the  leaves  of  an  oriental  shrub.  The  dry  leaves  con- 
tain about  13  per  cent  of  tannin  and  3  per  cent  of  caffein. 
Green  tea  is  produced  by  drying  the  leaves  rapidly  with 
artificial  heat,  and  with  the  loss  of  a  little  tannin.  Black 
tea  is  made  by  bruising  the  fresh  leaves  and  allowing  them 
to  ferment  before  drying.  In  this  treatment,  they  blacken, 
due  to  enzyme  action.  The  product  differs  from  green 
tea  by  containing  only  about  5  per  cent  of  tannin.     Coffee, 


Figure  101.     A  tea  farm  in  Jaoan.- 
Mrs.  F,  H.  King.) 


(Courtesy  of 


328  CHEMISTRY  OF  THE  FARM  AND  HOME 

the  husked  seed  of  a  tropical  evergreen  tree,  contains  con- 
siderable fat  and  carbohydrate.  Caffein  is  present  to  the 
extent  of  about  1  per  cent.  It  is,  therefore,  a  weaker  stimu- 
lant than  tea.  By  roasting,  the  "berry"  loses  most  of  its 
water,  while  its  soluble  carbohydrates  increase  about  ten- 
fold. Cocoa  and  chocolate  are  prepared  from  the  pod- 
enveloped  beans  of  a  tropical  American  tree.  The  beans 
contain  about  50  per  cent  of  fat.  After  husking,  they  are 
allowed  to  ferment,  which  reduces  their  bitterness  and 
acidity.  They  are  then  hardened  and  darkened  by  drying 
in  the  light.  Chocolate  is  prepared  by  removing  the  germs 
from  the  beans.  It  has  practically  the  same  composition 
as  the  latter.  Cocoa,  on  the  other  hand,  is  prepared  from 
the  residue  of  the  beans  left  after  extracting  part  of  the  fat 
to  form  cocoa  butter.  Its  chief  constituents  are  about  30 
per  cent  fat  and  10  per  cent  protein.  Hence,  it  has  a  lower 
food  value  than  chocolate.  Still,  even  when  made  with 
water,  it  has  about  four  times  the  value  of  tea  or  coffee. 
Cocoa  and  chocolate  contain  one  to  two  per  cent  of  caffein 
and  other  alkaloids. 

Having  compared  the  values  of  foods,  we  can  study  the 
principles  of  dietetics.  The  diet  of  common  individuals 
and  families  may  be  considered  from  two  chief  points  of 
view:     (1)  as  to  efficiency,  and     (2)  as  to  cost. 

Balancing  the  Diet.  Economy  alone,  irrespective  of 
the  standard  protein  and  fuel  values,  is  not  a  safe  basis  upon 
which  to  plan  a  diet.  Prolonged  feeding  of  some  single 
food  stuff  which  contributes  to  the  standard  requirements 
may  lead  to  ill  health.  Some  food  stuffs  which  appear  well 
by  these  same  standards  may  also  contain  poisonous  ingre- 
dients. Examples  of  these  sorts  of  food  troubles  are  the 
prevalence  of  the  disease  beri-beri  among  people  fed  too 
exclusively  upon  polished  rice,  and  occasional  poisoning  by 
mushrooms.  These  conditions  require  attention  to  what  is 
called  the  physiological  balance  of  foods.     This  means  the 


HUMAN  FOOD  AND  DIETETICS 


329 


balance   necessary    to    produce    good    health  and  growth. 

Acid  and  Base  Balance.  A  very  important  balance  to 
be  adjusted  in  human  foods  is  that  between  acid-forming 
elements,  as  sulphur,  and  base-forming  elements,  as  potas- 
sium. The  former  are  oxidized  to  acids  by  the  processes 
of  digestion  and  assimilation.  If  other  bases  are  lacking, 
ammonia  is  withdrawn  from  the  protein  of  the  body  to 
neutralize  these  acids  and  provide  for  their  excretion.  Such 
a  process  is  not  only  wasteful,  but  also  disturbs  the  health. 
Then,  too,  the  mother  and  young  growing  child  must  have 
the  necessary  balance  between  calcium  and  phosphorus 
in  order  that  they  may  produce  calcium  phosphate  of  the 
skeleton  and  milk.  Again  fatty  foods,  such  as  too  rich  milk, 
may  disturb  infants  by  the  removal  of  calcium  from  the 
body.  This  is  used  to  form  soaps,  in  which  the  excess  of 
fat  is  excreted. 

The  differences  between  food  stuifs  as  to  the  amounts 
of  acid-forming  and  base-forming  elements  which  they 
contain  are  shown  in  Table  XIV.  The  values  in  the  first 
column  express  the  excess  of  acid-forming  over  base-forming 
elements  in  portions  of  the  material  supplying  100  calories 
of  fuel  value.  The  second  column  expresses  the  opposite 
relation  for  the  same  amount  of  food.  The  figures  repre- 
sent cubic  centimeters  of  standard  (normal)  acid  or  alkali 

solution. 

Table  XIV — Acid-forming  and  Base-forming  Foods 


C.  C.  of  standard  acid 
in  100  calorie  portion 


C.  C.  of  standard 

alkali  in  100    calorie 

portion 


Acid-forming  Foods 

Lean  Beef 

Eggs 

Wheat  Flour.  . 
Base-forming  Foods 

Celery 

Potatoes 

Milk 

Corn 


10.0 
9.0 

2.7 


40.0 

10.5 

3.3 

0.6 


330 


CHEMISTRY  OF  THE  FARM  AND  HOME 


WHEAT 


POTATO 


737X 


3  83   CALORICS 
PER    POUND 


FUCL  VALUE 

WHOLE  EGG 


1750  CALORItS 
PCR     POUND 


rUEL  VALUE 


8-».(,^ 


2  90  CALORICS 
PER    POUND 


FUEL  VALUE 

NAVY  BEAN, DRY 


iS.kX 


IB.5X 


Sf-bZ 


CQUALS 
1000      CALORIES 


rutL  VALUE 
CAL0RIE5  PER  POUXO 


WATER 

CARBOHYDRATtS 

PROTEIN 

FAT 

ASH 


ruiL   VALUC 
CALORICS  fER  POUND 


Figure  102.     The  food  values  of  some  important  articles  of  human  food. 


HUMAN  FOOD  AND  DIETETICS 


331 


Is  it  necessary  to  emphasize  further  the  importance 
of  varying  the  diet  by  introducing  vegetables  and  fruits 
to  balance  meat  and  eggs? 

Economy  in  Cost  of  Diet.  A  few  years  ago  more  fuel 
value  could  be  obtained  for  ten  cents  in  milk,  beans  and 
flour  than  in  any  other  food  stuffs.  That  situation  is  even 
more  true  at  present.  Dr.  H.  W.  Wiley,  well-known  cham- 
pion of  pure  food  legislation,  points  to  the  cereal  grains 
and  their  products  as  the  sources  of  relief  from  ''the  high 
cost  of  living. '*  This  economic  condition  applies  especially 
to  the  great  mass  of  laboring  population. 

It  is  possible  to  economize  in  cost  while  still  securing 
food  values,  as  is  shown  by  a  comparison  of  two  families 
made  by  Professor  Snyder. 

The  chief  items  of  expense  of  the  first  family  were  bread, 
cake  and  pastry,  steaks  and  roasts,  and  canned  goods. 
Among  the  more  expensive  items  of  the  second  family  were 
steak  and  boiling  pieces,  butter  and  milk.  This  family 
made  its  bread  and  pastry,  cooked  oatmeal  instead  of  using 
patented  breakfast  foods,  and  substituted  homemade 
shortening  for  butter.  It  also  substituted  beans  and  cheese 
partly  for  meat,  and  ate  liberally  of  the  less  expensive 
vegetables  and  fruits.  A  comparison  of  the  food  values 
and  cost  per  week  follows.  It  shows  that  the  second  family 
obtained  a  larger  amount  of  nutrients  at  one  half  the  expense 
of  the  first. 
Table  XV — Comparison  of  Food  Values  and  Cost  for  Two  Families 


Family  1 
Family  2, 


Protein 
Pounds 


7.9 
10.6 


Fat 
Pounds 


14.0 
14.8 


Carbohydrates 
Pounds 


19.0 
26.4 


Cost 
Dollars 


22.45 
11.30 


Large  amounts  of  concentrated  food,  such  as  cheese, 
should  be  avoided.    They  place  too  much  tax  upon  the  di- 


SS2  CHEMISTRY  OF  THE  FARM  AND  HOME 

gestive  system.  One  must  consider  the  palatability  of  foods, 
as  well  as  their  economy  and  food  values.  This  is  especially 
true  of  the  diet  of  invalids,  who  frequently  require  either 
the  palatabiHty  or  the  ease  of  digestion  possessed  by  meat 
extracts  and  similar  foods.  In  such  cases,  unusual  lack  of 
economy  in  the  purchase  or  use  of  food  stuffs  may  be 
justified.  With  the  help  of  the  principles  and  tables  you 
have  now  studied,  it  would  be  well  to  plan  several  menus 
for  a  man  at  light,  and  also  at  severe  labor.  You  might 
also   plan   menus  for  your  own  family. 

Preservation  of  Food.  With  the  congestion  of  popula- 
tion in  our  cities,  the  preservation  of  food  becomes  a  neces- 
sary problem.  Meat  must  be  kept  fresh  and  edible  during 
storage  and  transportation.  Fruits  and  vegetables  also 
must  be  kept  available,  so  far  as  possible,  throughout  the 
year.  You  are  familiar,  probably,  with  the  great  import- 
ance of  storing  meats  by  refrigeration  in  the  big  packing 
industry.  This  does  not  entirely  check  changes  due  to 
enzymes,  but  it  prevents  the  growth  of  bacteria,  and  the 
meat  keeps  in  good  condition  for  long  periods.  It  is 
especially  important  that  bacterial  changes  be  prevented 
in  foods.  Besides  rendering  the  food  unwholesome  to  the 
taste,  powerful  poisons,  the  ptomaines,  are  formed  from  pro- 
teins. Sickness  and  even  death  have  been  caused  by  these 
substances  in  ice  cream,  meat  and  other  foods. 

Salt  and  sugar  have  been  commonly  used  as  preservatives 
in  the  form  of  brine  and  syrup.  These  preservatives  have 
Uttle  effect  upon  the  composition  of  meats,  fruits  and  veg- 
etables other  than  the  removal  of  a  good  deal  of  water. 
To  what  phenomenon  which  we  studied  in  connection  with 
plant  roots  is  this  due?  Food-destroying  organisms  cannot 
develop   in   these   strong   solutions. 

The  canning  industry,  now  grown  to  enormous  propor- 
tions, is  an  invaluable  method  of  preserving  vegetables 
and  fruits.     It  makes  possible  a  wide  distribution  and  use- 


HUMAN  FOOD  AND  DIETETICS 


333 


fulness  of  these  important  food  stuffs.  In  our  country, 
tomatoes,  sweet  corn  and  peas  lead  in  importance  of  the 
industry  in  the  order  named.  The  convenience  attending 
the  use  of  canned  goods  is  somewhat  offset  by  losses  of 
nutrients  in  the  wash  water.  With  peas,  for  example, 
while  the  water  content  increases  from  about  80  to  85  per 


Figure  103.     The  "Squirrel  Cage"  of  a  canning  factory.     The  peas  are  sorted 
by  size  in  the  revolving  screen. 

cent  during  canning,  the  carbohydrates  decrease  from 
about  64  to  61  per  cent  of  the  dry  peas.  This  loss  is  chiefly 
due  to  extraction  of  sucrose  by  the  wash  water. 

The  pectin  compounds  have  interesting  and  important 
relations  to  the  making  of  fruit  jellies.  By  boiling  the 
immature  fruits  in  water,  pectose  is  changed  to  pectin. 
On  cooling,  this  sets  to  a  semi-solid  mass  and  gives  the 
''body"  so  much  esteemed  in  jelly.  An  average  is  struck 
between  food  value  and  jellying  quality  by  selecting  the 
fruit  at  early  ripeness. 


334  CHEMISTRY  OF  THE  FARM  AND  HOME 

The  principle  of  the  canning  industry  is  the  kilHng  of 
bacteria  and  molds  by  heat  and  excluding  them  thereafter 
by  tightly  sealing  the  containing  jars.  The  fact  that  high- 
grade  products  can  be  produced  only  from  wholesome 
material  and  by  cleanly  methods  gives  the  canning  industry 
special  merit. 

Drying  is  a  very  old  and  very  effective  means  of  preserv- 
ings meats,  fruits,  and  other  foods.  By  thus  reducing  the 
water  content  to  a  low  percentage,  the  growth  of  organisms 
which  cause  decay  is  prevented.  Vinegar  acts  as  a  preserva- 
tive by  virtue  of  its  acidity,  which  few  organisms  can  endure. 

Chemical  preservatives,  as  you  know,  have  been  the 
great  ''bone  of  contention"  for  several  years  between  food 
manufacturers  and  executives  of  the  food  laws.  Among 
these  preservatives,  sodium  borate,  or  borax,  and  sodium 
sulphite  have  been  added  to  meat  and  milk.  Formaldehyde, 
or  formalin,  has  been  added  to  milk;  and  the  sodium  salts 
of  two  organic  acids,  benzoic  and  saUcylic,  have  been  added 
especially  to  fruit  products.  The  use  of  the  latter  has 
been  justified  by  some  persons  on  the  ground  that  they 
occur  naturally  in  certain  fruits.  Some  preservatives, 
when  consumed  by  healthy  persons  in  the  small  amounts 
one  would  possibly  obtain  in  preserved  foods,  have  been 
found  not  to  be  appreciably  injurious.  It  is  possible  that 
some  weak  systems  would  be  unfavorably  affected  by 
continued  eating  of  such  foods.  The  use  of  preservatives  is 
undesirable,  because  it  makes  possible  the  canning  and  sale 
of  stale  and  unfit  material  which  would  otherwise  quickly 
disclose  its  condition  by  decay.  The  use  of  most  of  them 
is  now  prohibited  by  law.  The  preservation  of  ''smoked" 
meats  by  creosote  compounds  of  the  smoke  is  virtually 
a  chemical  method.  Copper  salts  have  sometimes  been 
used  to  color  vegetables  and  improve  their  appearance. 
Their  use  is  now  prohibited  by  the  national  food  laws. 
It  is  well  to  remember  that  copper,  aluminium  and  especially 


HUMAN  FOOD  AND  DIETETICS  335 

lead  compounds  are  poisonous  when  eaten  in  appreciable 
quantities.  Hence,  one  should  avoid  cooking  or  storing 
strongly  acid  food  stuffs  in  vessels  of  the  metals. 

Two  types  of  food  label.  The  dairy  and  food  laws  of  a 
certain  state  provide  a  penalty  for  the  making  or  selling  of 
baking  powders  in  packages  not  plainly  labeled  with  the 
commonly  known  names  of  the  ingredients  contained 
therein.  The  essential  parts  of  labels  from  the  packages  of 
two  different  manufacturers  of  baking  powders  are  given. 
Observe  how  A  warps  the  truth.  The  objections  to  alum 
are  mentioned  in  the  text. 

A  B 

No  Alum     No  Ammonia  This  baking  powder  is  composed 

remains    in    food  prepared   with  of  the  following  ingredients  and 

Baking  Powder  none  other:     Bicarbonate  of  soda, 

Sisbaking'powder  is  composed      ±fT.\Z'L^^hS^^c!tl^J^"' 
of  the  following  ingredients  and      «*^'^^'  ^^^"^  ^^^  ^^'^  ^^  ^^g^- 
none    other:     Soda,    acid    phos- 
phates, com  starch,  sodic  aluminic, 
sulphate  and  white  of  egg. 

Pure  Food  Laws.  The  certainty  of  purchasing  pure 
and  wholesome  foods  at  market  is  being  made  continually 
stronger  by  the  creation  and  operation  of  food  laws. 
Chemical  analysis  is  the  "court  of  last  resort"  as  to  whether 
or  not  foods  are  adulterated.  In  the  case  of  many  mat- 
erials, as  spices,  beverages  and  cereal  products,  the  micro- 
scope offers  a  means  of  rapid  detection  of  impurity  or  fraud. 

SUMMARY 

The  food  requirements  of  man  are  more  varied  than  those  of  the 
lower  animals.  Like  the  other  animals,  however,  he  needs  a  certain 
amount  of  protein  for  growth  and  repair.  He  needs,  too,  increasing 
amounts  of  carbohydrates  and  fat  in  proportion  to  his  muscular  activity. 
Meat,  fish  and  eggs  supply  chiefly  protein,  while  the  cereal  grains 
supply  the  necessary  fuel  values  for  muscular  work.  In  proportion 
to  their  weight,  children  require  much  more  of  these  food  compounds 
than  adults. 

Vegetables  and  fruits  are  of  value  for  their  laxative  and  flavoring 
effects.    They  also  supply  basic  elements,  which  neutralize  the  acid 


336  CHEMISTRY  OF  THE  FARM  AND  HOME 

elements  of  meat  and  eggs.  By  the  latter  use  they  spare  the  valuable 
protein  compounds. 

Cooking  does  not  change  the  composition  of  meats  appreciably, 
though  it  adds  to  their  flavor.  Compounds  extracted  by  water  in  boil- 
ing or  stewing  are  kept  in  the  meat  by  roasting  or  frying.  The  making 
of  breads  includes  fermentation  produced  by  yeast  acting  upon  carbo- 
hydrates. The  carbon  dioxide  produced  in  this  way  swells  the  dough, 
which  owes  its  elasticity  to  the  proteins  of  the  gluten.  By  baking,  some 
cf  the  starch  is  converted  to  soluble  or  volatile  compounds  which  pro- 
duce flavor. 

Canning  makes  possible  a  wide  use  of  important  food  materials 
at  a  small  loss  of  food  value.  It  depends  upon  the  kiUing  of  decay- 
producing  organisms  in  wholesome  materials  and  excluding  their 
further  entrance.  Drying  is  a  very  effective  means  of  preservation. 
The  use  of  chemical  preservatives  is  of  questionable  character.  This 
is  chiefly  because  it  favors  the  use  of  unwholesome  food  materials. 

The  proper  balancing  of  protein  and  fuel  values  requires  careful 
consideration  of  efficiency  and  economy.  One  must  also  meet  special 
requirements  of  the  body  by  a  variety  of  food  selection.  The  pure 
food  laws  assist  one  to  obtain  pure  and  wholesome  food  stuffs. 

QUESTIONS 

1.  What  is  dietetics? 

2.  Why  does  the  feeding  oi  man  require  special  attention? 

3.  What  is  the  largest  factor  producing  fuel  requirement  in  man 
when  awake? 

4.  What  two  factors  make  the  fuel  requirement  of  children  high? 

5.  What  are  the  chief  compounds  supplying  energy  or  fuel  value 
in  foods? 

6.  Is  sufficient  protein  supplied  by  a  quantity  equal  to  that 
lost  by  wear  from  the  body  of  an  adult? 

7.  What  are  the  average  amounts  of  protein  and  of  energy 
consumed  by  a  man  daily? 

8.  Name  three  food  stuffs  which  supply  chiefly  protein?  Three 
which   supply   energy? 

9.  What  are  two  chief  values  of  vegetables  and  fruit  in  diet? 

10.  What  important  chemical  element  is  largely  removed  in 
making  flour  from  wheat? 

11.  What  is  the  composition  of  wheat  gluten? 

12.  What  compounds  are  formed  or  added  in  manufacturing 
breakfast  foods? 

13.  What  compounds  produce  flavor  in  fruits? 

14.  By  what  changes  is  cider  produced?     Vinegar? 

15.  What  difference  in  effect  upon  the  composition  of  meat  is 
produced  by  boiling  as  compared  with  frying? 

16.  Does  pasteurization  affect  the  digestibility  of  milk? 


HUMAN  FOOD  AND  DIETETICS  337 

17.  How  is  the  raising  of  bread  dough  caused  by  yeast?     By 
baking  powder? 

18.  What  chemical  changes  occur  in  the  baking  of  bread? 

19.  Why  is  soup-making  preferable  to  stewing  or  boiling  vege- 
tables? 

20.  What  method  of  cooking  retains  the  most  food  value  in  the 
potato? 

21.  What  is  the  cause  of  changes  of  composition  in  stored  vege- 
tables? 

22.  What  change  occurs  in  potatoes  kept  near  freezing? 

23.  What  compounds  produce  the  flavor  of  spices? 

24.  What  compound  gives  stimulant  action  to  tea  and  coffee? 

25.  How  is  black  tea  prepared?     Coffee? 

26.  What  are  the  chief  constituents  of  cocoa? 

27.  What  is.  meant  by  the  physiological  balance  of  foods? 

28.  Name  one  important  balance  of  this  kind. 

29.  What  is  the  objection  to  an  excess  of  acid-forming  elements 
in  the  ration? 

30.  Name   one   high   acid-forming   and   one   high   base-forming 
food  stuff. 

31.  What  food  stuffs  would  you  select  in  planning  a  menu  so 
as  to  be  economical  of  cost? 

32.  How  does  refrigeration  act  in  preserving  foods? 

33.  How  do  salt  and  sugar  act  as  preservatives? 

34.  Upon  what  chemical  change  is  jelly-making  dependent? 

35.  What  are  the  beneficial  effects  of  canning  food  stuffs?     Of 
drying? 

36.  Why  is  the  use  of  chemical  food  preservatives  undesirable? 

37.  Why  should  one  avoid  cooking  acid  food  stuffs  in  copper 
or  aluminum  vessels? 

38.  By  what  two  scientific  means  are  the  pure  food  laws  made 
effective? 


CHAPTER  XIV 

MISCELLANEOUS    MATERIALS   OF   IMPORTANCE 
IN  DAILY  LIFE 

Suppose  you  were  asked  to  name  some  material  common 
to  daily  life  but  entirely  free  from  any  relations  to  the 
science  of  chemistry.  Would  that  not  be  a  quite  hopeless 
task?  One  cannot  avoid  the  realization  that  chemical  com- 
position is  responsible  for  the  valuable  properties  of  many 
common  things  about  us.  Moreover,  in  the  preparation 
or  use  of  many  of  these  things  interesting  and  important 
chemical  reactions  occur.  Let  us  select  some  of  the  materials 
most  useful  in  daily  life  and  dependent  upon  principles  of 
chemistry  for  their  preparation  and  properties.  Some  of 
these  will  be  especially  useful  in  the  home,  others  about  the 
farm.  Among  them  are  cloth  fabrics,  materials  for  the  con- 
struction of  dwellings  and  agents  for  warring  upon  insect 
and  fungus  enemies  of  plants.  Knowledge  of  the  composi- 
tion and  action  of  these  materials  will  increase  the  interest 
and  efficiency  of  the  housewife  and  farmer  in  their  work. 

Next  in  importance  to  man  after  food  are  clothing  and 
shelter.  Clothing,  as  you  know,  is  made  from  cloth  fabrics 
manufactured  from  certain  plant  and  animal  fibers.  The 
most  useful  of  the  plant  fibers  are  cotton,  flax  and  hemp. 
Wool  and  silk  are  the  chief  fibers  obtained  from  animals. 

Cotton  is  used  in  greater  quantities  than  the  other  plant 
fibers.  It  is  the  hairy  fiber  attached  to  the  seeds  of  several 
varieties  of  plants  belonging  to  a  single  large  family.  Our 
country  leads  the  world  in  the  production  of  cotton.  The 
variety  grown  in  the  southern  states  is  a  low  shrub  whose 
pods  or  * 'bolls"  mature  in  December  to  January.  It  yields 
about  300  pounds  of  impure  cotton  or  *'lint"  per  acre.  Over 
three  million  tons  of  the  fiber  are  produced  yearly  in  the 

338 


MISCELLANEOUS  MATERIALS 


339 


Figure  104.     Drawings  from  microphotographs  of  cloth 
fibers.     From  left  to  right:  wool,  cotton,  silk,  flax. 


United  States.  By  the  use  of  the  ginning  machine  the 
seeds  are  removed  from  the  fiber.  The  former  yield  the 
cottonseed  oil  of  commerce. 

Cotton  fiber  is  the  purest  form  of  cellulose  found  in 
nature.  Each  fiber  is  about  an  inch  long  and  one  thousandth 
of  an  inch  in  diameter.  It  is  flattened  or  collapsed,  and 
spirally  twisted,  as  shown  in  Figure  104.  Its  fibers  are  thus 
well  suited  for  spinning  into  threads,  on  account  of  the 

natural  inter- 
locking of  the 
fibers.  Very  short 
cotton  is  twisted 
into  yarn.  A 
certain  water 
content  of  cot- 
ton fiber  is  nec- 
essary for  good 
spinning  quality.  Too  much  makes  it  sticky,  while  too 
little  makes  it  brittle  and  weak.  As  it  contains  only  5  per 
cent  or  less  in  the  bale,  it  is  usually  necessary  to  moisten 
the  fiber  in  the  spinning  rooms.  Lancashire,  England,  has  a 
climate  very  favorable  to  good  working  quality  of  cotton. 

The  thread  is  whitened  by  boiling  with  steam,  treating 
with  bleaching  powder  and  washing  with  soap.  It  is  then 
''sized'*  by  soaking  it  in  starch  paste.  This  increases  its 
weight  and  strength.  If  it  tends  to  be  brittle,  it  is  dipped 
in  either  tallow  or  paraffin.  Cotton  fabric  is  woven  by  ma- 
chinery by  crossing  weft  or  "woof"  threads  alternately  over 
and  under  long  parallel  threads  called  the  warp.  The  raw 
cloth  is  bleached  by  bleaching  powder  and  alkalies.  This  treat- 
ment dissolves  grease  and  converts  incrusting  compounds  to 
soluble  forms.  It  is  then  weighted  by  starch  paste,  with  or 
without  clay.     This  process  is  called  "calendering." 

Mercerized  cotton  is  made  by  treating  cotton  first  with 
strong  alkaU  and  then  with  sulphuric  acid.     The  process  is 


340      CHEML^TRV  OF  TKE  FARM  AND  HOME 

named  from  John  Mercer,  who  discovered  the  contracting 
and  clearing  effect  of  alkali  upon  cotton  fibers.  The  alkali 
removes  the  outer  surface  of  the  fiber  and  swells  it  to  round, 
cyHndrical  form.  Can  you  not  suggest  what  corrective 
effect  the  acid  treatment  has  in  following  the  alkali?  The 
product  is  stretched  while  still  gelatinous  from  the  treat- 
ment. Mercerized  cotton  is  heavier  and  stronger  than  the 
untreated  fiber  and  has  a  silky  luster.  The  luster  is  pro- 
duced by  reflection  of  light  from  the  rounded  fibers. 

Artificial  silk  is  made  from  collodion,  which  is  a  solution 
of  nitro-cellulose  or  gun  cotton  in  ether.  This  is  the  solu- 
tion called  ''new  skin,"  used  for  covering  cuts  and  bruises. 
Nitro-cellulose  is  made  by  treating  cotton  with  a  mixture 
of  strong  nitric  and  sulphuric  acids.  It  is,  as  you  know, 
the  basis  of  powerful  explosives,  and  very  inflammable.  Col- 
lodion is  squirted  into  dilute  nitric  acid  in  fine  streams 
which  harden  to  threads.  The  product  is  then  treated  with 
reducing  agents,  which  greatly  decreases  its  inflammabihty. 
This  artificial  silk  is  weaker  and  less  elastic  than  silk.  It 
chews  to  a  pulp,  while  the  latter  falls  apart. 

Flax,  or  linen,  is  the  most  important  spinning  fiber,  next 
to  cotton.  It  is  obtained  from  a  shrub  which  thrives  in 
cooler  climates  than  cotton.  Russia  produces  over  one 
half  the  world's  supply,  but  Belgium  and  Ireland  grow  the 
best  quaUty.  The  crop  is  harvested  and  dried  just  as  it 
begins  to  turn  brown.  The  fibers  are  then  separated  from 
the  wood  of  the  stem  by  the  process  called  ''retting,"  which 
is  a  bacterial  fermentation  produced  by  soaking  in  water. 
Certain  enzymes  of  the  bacteria  destroy  the  pectin  com- 
pounds which  incrust  the  fibrous  cells  of  the  stem  and  bind 
them  together.  The  retted  stalks  are  crushed  and  the  fibers 
combed  out.  These  form  about  thirty  five  per  cent  of  the 
stem.  They  are  bleached  in  the  same  manner  as  cotton. 
Each  fiber  is  a  plant  cell  having  the  form  of  a  long,  cylindrical, 
untwisted,  thick-walled  tube,  with  closed  ends.     While  less 


MISCELLANEOUS  MATERIALS  341 

elastic  than  cotton,  it  takes  a  fine  polish  when  starched  and 
ironed,  on  account  of  its  very  smooth  surface.  Hence  the 
high  favor  of  fine  linens. 

Hemp  yields  a  coarse  fiber  unsuitable  for  cloth  fabrics. 
The  resistance  of  this  fiber  to  decay  in  water  and  its  great 
strength  make  it  valuable  for  twine,  rope  and  sacking.  The 
plant  is  a  slender  shrub,  eight  feet  or  more  in  height,  adapted 
to  mild  climates.  The  central  states  of  this  country,  includ- 
ing Kentucky,  Illinois  and  Missouri,  form  a  hemp-growing 
region.  Hemp  fiber  is  an  unbleachable,  ligno-cellulose.  The 
strongest  ropes  are  made  from  manila  hemp,  obtained  from 
the  petiole  of  a  species  of  banana  in  the  Philippine  Islands. 

Wool  is  a  fine,  soft  grade  of  hair.  Some  goats,  as  the 
cashmere,  produce  long,  soft  hair  prized  for  cloth-making. 
As  you  see  by  Figure  104,  wool  has  a  rough,  scaly  covering. 
Its  strength  is  due  to  the  cortex,  the  portion  between  the 
covering  and  the  pith .  A  special  machine  is  used  for  testing 
the  breaking  strength  of  the  wool  fibers.  Our  leading  sheep- 
raising  states,  Wyoming  and  Montana,  support  about  four 
and  a  half  million  head  of  sheep  each.  Billings,  Montana,  is 
said  to  be  the  greatest  wool-shipping  center  of  the  world. 
The  average  weight  of  a  fleece  is  eight  pounds,  but  on  the 
ranges  of  alkali  soils  the  weight  is  much  less.  The  latter 
wools  are  also  of  poor  quality,  due  to  the  destructive  action 
of  the  soil  dust  on  the  fiber.  The  total  wool  clip  of  this 
country  in  1909  was  estimated  as  worth  the  enormous  sum 
of  seventy-eight  million  dollars. 

Raw  wool  is  very  greasy  and  dirty  on  account  of  the  natur- 
al oily  secretion  or  yolk  of  the  sheep's  skin  and  the  residues 
from  perspiration.  The  whole  material,  called  suint,  is 
removed  by  washing  the  wool  in  alkali.  The  burrs  and  other 
dirt  are  removed  by  charring  with  acid,  drying  and  shak- 
ing. Long-staple  wools  have  fibers  one  and  a  half  or  more 
inches  long.  Like  other  hair,  wool  is  a  protein  compound. 
It  differs  from  albumin  of  the  blood  chiefly  by  containing 


342 


CHEMISTRY  OF  THE  FARM  AND  HOME 


SL  little  less  carbon  but  more  sulphur.  It  has  a  remarkable 
affinity  for  water,  which  makes  it  liable  to  adulteration. 
As  much  as  fifty  per  cent  may  be  present  without  producing 
a  moist  feeling. 

Silk  is  the  secretion  from  which  the  silk  worm  makes  its 
cocoon.  In  China  and  India  the  wild  worms  feed  on  oak 
leaves.  The  domesticated  worms  are  fed  on  mulberry  leaves. 
At  hatching  they  are  no  larger  than  pin  heads.     In  the 

oriental  c  o  u  n  - 
tries  the  eggs  are 
sometimes  car- 
ried on  the  hu- 
man body  for 
hatching.  The 
worms  grow  rap- 
idly to  a  length 
of  about  three 
inches,  when 
they  spin  the 
cocoon.  Before 
they  can  pupate 
and  emerge  as 
moths  they  are  killed  by  heat.  The  gum  by  which  the  fiber 
is  cemented  is  softened  by  warm  water  and  the  thread  is 
unwound.  It  is  a  more  slender  fiber  than  cotton,  but  its 
length,  from  a  single  cocoon,  may  reach  two  thousand  yards. 
Several  fibers  are  wound  together  to  form  a  thread.  In 
1907  Europe  used  twenty-five  million  and  our  country  used 
fifteen  million  pounds  of  raw  silk.  China  furnishes  one 
half  the  world's  supply,  and  Japan  and  Italy  each  furnish 
about  one  fourth.  Like  wool,  silk  is  a  protein  compound. 
Satin  is  made  by  weaving  cotton  weft  on  silk  warp. 

The  extensive  dyeing  industry  has  risen  from  the  demand 
for  beautifying  cloth  and  textiles.  In  ancient  times  dye- 
stuffs  were  obtained  chiefly  from  plants.     There  was  the 


Figure  105.     Feeding  silk  worms  in  Japan. 

From  Kind's  "Farmers  of  Forty  Centuries"  by  permission. 


MISCELLANEOUS  MATERIALS  343 

red  of  madder,  the  yellow  of  crocus  and  the  blue  of  indigo. 
The  famous  purple  of  Tyre  was  prepared  from  a  secretion 
obtained  from  shellfish  still  found  in  the  Mediterranean 
Sea.  Only  a  few  drops  of  the  prized  secretion  were  obtained 
from  each  fish.  The  American  colonists  dyed  with  metals. 
Iron  buff,  for  example,  was  obtained  by  impregnating  the 
fabric  first  with  ferric  acetate  solution  and  then  with  the 
leachings  of  wood  ashes.  What  familiar  iron  compound 
would  be  formed  in  the  fiber  by  this  treatment?  Man- 
ganese brown  was  similarly  made  from  potassium  perman- 
ganate. The  fabrics  were,  of  course,  finally  washed  free 
from  soluble  salts.  Most  of  these  dyes  were  far  from 
satisfactory.  Either  they  were  too  loosely  held  or  "fixed," 
by  the  fabrics  or  they  lacked  endurance,  or  * 'fastness, '^  to 
light  and  washing. 

Coal  tar  dyes,  however,  possess  fastness  to  a  high  degree. 
The  discovery  and  development  of  these  compounds  has 
furnished  material  for  one  of  the  most  fascinating  chapters 
in  the  history  of  chemistry.  In  1856  a  young  English 
chemist  was  attempting  to  make  the  alkaloid  quinine 
from  aniline.  The  latter  is  a  nitrogen-containing  derivative 
of  benzene,  which  is  a  hydrocarbon  forming  the  basis  of  the 
coal  tar  compounds.  Instead  of  quinine  a  beautiful  violet 
dye  was  obtained.  A  few  years  later  the  discovery  of 
alizarine  among  the  products  obtained  from  benzene  opened 
up  the  wonderfully  fertile  field  of  work  of  synthesizing  the 
aniline  or  coal  tar  dyes.  Over  fourteen  thousand  of  these 
compounds  have  been  produced  from  the  tar  which  once 
appeared  to  be  a  useless  waste  product  in  the  production 
of  illuminating  gas  from  coal.  The  young  chemist  who  be- 
gan this  work,  or  the  late  Sir  William  Perkin,  has  been 
highly  and  fittingly  honored  the  world  over. 

The  aniline  dyes  are  divided  into  those  of  acid  and  those 
of  basic  character.  This,  at  once,  suggests  that  their  fixa- 
tion may  be  of  chemical  nature,  as  indeed  it  is.     Basic  dyes 


344  CHEMISTRY  OF  THE  FARM  AND  HOME 

fix  directly  on  wool  and  silk,  that  is,  the  fabrics  dye  by  mere 
immersion  in  the  dyeing  fluid.  This  is  because  the  animal 
fibers  are  slightly  acid  in  nature.  Acid  dyes,  however, 
fix  on  these  fibers  only  from  baths  to  which  acid  has  been 
added.  They  require  precipitation  on  or  in  the  fiber,  as 
it  were,  by  stronger  acids.  JMethyl  violet  and  Bismarck 
brown  are  basic   dyes. 

The  vegetable  fibers  are,  for  the  most  part,  quite  neutral 
to  dyes.  When  a  dye  is  taken  up  directly  by  plant  or  animal 
fibers  it  is  called  a  ''direct"  dye.  Congo  red  was  the  first 
discovered  of  the  direct  dyes.  It  was  observed  that  solu- 
tions of  the  dye  filtered  through  paper  leave  the  paper  dyed. 
The  plant  fibers  generally  require  mordanting  to  fix  dyes. 
Clay  and  aluminium  oxide  are  common  mordants.  In  some 
way  these  substances  when  suspended  in  the  fabric  increase 
the  aflfinity  between  the  fibers  and  the  dye.  A  dye  requiring 
the  use  of  mordants  is  called  "substantive."  Basic  dyes 
fix  on  plant  fibers  when  tannic  acid  or  oil  are  used  as  mor- 
dants.   They  are  not  so  fast  as  the  acid  dyes. 

Dyeing  requires  previous  careful  cleaning  of  the  fabrics. 
Silk  is  prepared  by  removing  its  natural  gum  with  soap. 
Its  fixing  power  is  increased  by  soaking  in  ferric  nitrate 
solution  or  weak  acetic  acid.  Then  it  is  immersed  in  a 
solution  of  the  dye  with  dilute  sulphuric  acid.  Sometimes 
it  is  also  immersed  in  solution  of  tin  chloride  until  its  weight 
increases  several  fold.  Finally  it  is  made  lustrous  and  elas- 
tic by  oiling.  Cotton  and  linen  can  be  cleaned  by  soap  and 
dilute  alkali.  Direct  dyes  fix  best  on  these  fibers  when 
such  salts  as  sodium  chloride  or  sulphate  are  present. 

Fastness  of  dyes  to  fight  is  tested  by  stretching  the 
dyed  fabric  across  a  small  opening  in  the  shutter  of  a  south 
window.  If  the  color  of  the  exposed  area  fades  in  one  week 
or  less  the  dye  is  regarded  not  fast.  If  four  weeks  or  longer 
is  required  to  produce  fading,  the  color  is  regarded  as  fast. 
Fastness  to  soap  is  tested  by  beating  the  dyed  fabric  to 


MISCELLANEOUS  MATERIALS  345 

140°F.  in  a  strong  bath  of  laundry  soap.  Skeins  of  cotton 
and  of  silk,  thoroughly  cleaned  from  grease  and  dirt,  are 
immersed  with  the  fiber.  If  only  the  soap  solution  is  colored, 
the  dye  is  regarded  as  fast.  If  either  skein  is  colored,  the 
dye    is    not    fast. 

Cleaning  of  fabrics,  especially  the  removal  of  various 
stains,  is  an  ever  practical  problem  of  the  housewife.  It 
also  involves  the  use  of  chemical  properties  and  reactions. 
Commercial  cleansing  is  roughly  divided  into  dry  cleaning 
and  spot  cleaning.  The  former  is  also  called  chemical  or 
French  cleaning.  It  is  a  chemical  process  in  the  sense  that 
solvents  for  fats  and  mineral  oils  are  used  to  remove  grease. 
It  is  dry  in  the  sense  that  these  solvents  are  liquids  other 
than  water.  Benzine,  benzol  and  chloroform  are  the  sol- 
vents generally  used.  The  first  is  a  mixture  of  hydrocarbons 
related  to  kerosene  and  paraffine.  The  second  is  the  foun- 
dational hydrocarbon  of  coal  tar  oil.  The  last  is  a  deriva- 
tive of  the  simplest  hydrocarbon  related  to  paraffine. 
Carbon  bisulphide  and  other  solvents  which  might  be  used 
are  either  too  expensive  or  have  disagreeable  odors.  Benzine 
is  both  volatile  and  very  inflammable.  Would  you  regard 
it  desirable  for  use  in  open  tubs?  On  the  commercial 
scale  the  clothing  is  treated  in  closed  tumbling  machines 
which  remove  the  dirt  by  agitation,  while  preventing  loss 
of  the  solvent  by  evaporation.  Some  pure  soap  is  added 
to  the  cleaning  fluid.  Some  of  these  machines  are  so  made 
that  the  chamber  can  be  filled  with  carbon  dioxide.  How 
would  this  decrease  the  fire  risk?  The  dry  cleaning  method 
is  necessary  for  the  cleaning  of  white  leather  goods,  which 
are  tanned  with  alum,  because  water  is  injurious  to  such 
goods  by  its  solvent  action. 

Spot  cleaning  includes  the  removal  of  stains  due  to  pitch, 
paint,  fruit  juice,  itik  and  such  substances.  Wood  alcohol, 
with  soap  and  a  very  little  ammonia,  is  effective  in  removing 
paint,  pitch  and  tar.    One  should  always  test  the  fastness 


346  CHEMISTRY  OF  THE  FARM  AND  HOME 

of  the  dye  to  such  cleansers  by  treating  a  bit  of  the  fabric 
before  proceeding  with  the  work.  Violet  and  green  dyes  are 
injured  by  wood  alcohol.  Since  paints  are  bound  or  "set" 
by  Unseed  oil,  they  can  be  removed  by  the  same  solvents 
used  for  grease.  Benzine  and  benzol  are  good  cleansers 
for  paint,  pitch  and  tar.  Turpentine  is  especially  useful 
for  paint  and  pitch.  Aniline  is  the  best  solvent  for  varnish 
and  resin.  Common  ink  is  iron  tannate.  It  is  dissolved 
by  certain  organic  acids  such  as  acetic  and  oxalic  acids. 
Salts  of  these  acids  are  also  helpful.  How  would  you 
explain  the  action  of  the  home  agents,  lemon  juice,  vinegar 
and  cream  of  tartar,  for  removing  ink  stains?  Indelible  inks 
are  made  from  aniline  dyes,  for  which  aniline  is  the  uni- 
versal solvent.  Iron  rust  or  mold  can  be  dissolved  com- 
pletely only  by  dilute  mineral  acids,  though  the  organic 
acids  are  useful.  After  using  any  of  these  stain  removers 
it  is  well  to  soak  the  fabric  in  weak  mineral  acid.  Finally, 
of  course,  the  fabrics  must  be  thoroughly  washed.  Grass 
stains,  due  to  chlorophyll,  should  be  removed  by  common 
alcohol.  Blood  is  not  soluble  in  the  fat  solvents.  Like 
other  soluble  protein  materials,  it  dissolves  better  in  cold 
than  in  hot  water.  This  is  because  heat  coagulates  soluble 
proteins.  On  the  other  hand,  the  colored  compounds  of 
fruit  stains  are  more  soluble  in  hot  than  in  cold  water. 

Bleaching  is  frequently  necessary  to  complete  the  remov- 
al of  stains,  especially  of  grass,  blood  and  fruit  stains.  This 
is  practically  an  oxidation  of  colored  to  colorless  compounds. 
For  this  purpose  immersion  in  solution  of  bleaching  powder 
or,  better,  of  the  related  sodium  hypo-chlorite,  is  beneficial. 
Potassium  permanganate  is  safer  than  the  chlorites  for  use 
on  wool  or  silk.  It  is  necessary  to  follow  with  an  acid  solvent 
to  remove  the  manganese.  The  bluing  of  white  fabrics 
in  washing  is  merely  a  process  of  weakening  other  colors,  such 
as  yellow,  by  blue.  The  common  bluing  compounds  are 
indigo  and  aniUne  dyes.     Old  fashioned  bluing  was  an  iron 


MISCELLANEOUS  MATERIALS  347 

compound,  which  sometimes  left  rust  spots  on  the  cloth. 
Sodium  peroxide  is  also  used  as  a  bleaching  agent.  Per- 
haps the  safest  efficient  bleach  is  produced  by  chlorine  re- 
leased electrolytically  from  salt  solution  in  which  the  fabric 
is  suspended.  What  have  you  previously  learned  to  be 
the  active  agent  in  bleaching  by  chlorine? 

Paints  and  varnishes,  in  relation  to  their  composition 
and  durability,  are  materials  of  vital  concern  to  the  farm 
and  home.  It  is  desirable  to  secure  the  longest  life  and 
most  efficient  protection  against  the  weather  from  exterior 
coatings  of  paint.  The  housewife  should  know  also  what 
methods  of  cleaning  can  be  appUed  safely  to  interior  finishes. 
For  many  years  lead  white  has  been  the  standard  body 
material  for  paints  applied  to  exterior  woodwork.  This 
is  basic  lead  carbonate,  which  contains  more  lead  than  the 
common  carbonate.  Paint  bodies  of  this  sort  are  spread 
by  mixing  with  linseed  oil  and  ''cutting"  or  thinning  with 
turpentine.  The  thinned  oil  deposits  the  pigment  in  the 
surface  tissue  of  the  wood.  The  thinner  then  evaporates 
and  the  oil  dries  and  ''sets"  the  paint,  forming  a  protecting, 
skin-like  coat.  By  referring  to  the  chapter  on  the  plant  and 
its  products  you  will  recall  what  chemical  change  causes 
the  hardening  of  the  oil.  Boiled  oil  sets  more  rapidly  than 
raw  oil  and  hence  is  less  penetrating.  It  is  thus  unsuited 
for  the  first  or  "priming"  coats.  Lead  is  not  fit  for  use  inside 
chemical  laboratories,  where  hydrogen  sulphide  is  present 
in  the  air.  In  such  places  zinc  oxide  is  used  to  replace  the 
lead.  What  compounds  of  lead  and  zinc  are  formed  by  the 
action  of  the  hydrogen  sulphide  gas  on  these  paints?  The 
compound  formed  from  lead  is  black  while  that  from  zinc 
is  white,  so  that  zinc  white  is  least  injured  by  hydrogen 
sulphide.  Other  colors  than  white  are  obtained  by  mix- 
ing carbon  black  and  various  colored  pigments  with  the 
lead  or  zinc.  Thus  lead  chromate  gives  yellow,  chromic 
oxide  gives  green,  ferrous  ferrocyanide  gives  blue,  and  so 


348  CHEMISTRY  OF  THE  FARM  AND  HOME 

on.  The  best  vehicle  for  lead  is  a  thinner  composed  of  95 
parts  Hnseed  oil  and  5  parts  turpentine.  Japans  or  ''driers'^ 
are  often  mixed  with  paints  to  hasten  their  drying.  These 
are  compounds  of  lead  or  manganese  with  oil  or  resin.  They 
assist  in  the  oxidations  which  produce  the  drying. 

Paints  are  of  great  service  in  protecting  bridges  and  other 
steel  structures,  as  well  as  steel  and  iron  tools,  from  de- 
struction by  rusting.  For  such  surfaces  ferric  oxide  is 
mixed  in  oil  with  other  inert  materials,  such  as  calcium 
carbonate  and  clay.  Venetian  red  and  Prince's  metaUic 
are  made  in  this  way.  Small  articles  are  dipped,  while 
large  surfaces  are  sometimes  sprayed  with  the  paint.  The 
brown  color  of  umber  and  of  sienna  are  due  to  the  addition 
of  a  small  amount  of  manganese  oxide  to  the  iron  oxide. 
Salts  of  casein  with  sodium  and  other  bases  are  the  pig- 
ments of  casein  paints. 

Ready  mixed  paints  are  products  of  a  great  industry, 
built  on  the  extensive  need  for  paints.  It  was  estimated 
that  in  1907  seventy  million  gallons  of  such  paints  were 
used  in  the  United  States.  Unprincipled  manufacturers 
have  sometimes  attempted  to  profit  from  adulteration  of 
these  materials.  Such  cheap  materials  as  chalk,  gypsum 
and  clay  have  been  substituted  for  lead.  In  lawful  trade 
zinc  oxide  is  mixed  with  white  lead  to  make  leaded  zincs  and 


Figure  106.      The   durability   of  house  paints  exposed  to  the  weather.     The 
paint  on  the  right  contained  too  much  zinc  and  too  little  lead. 


MISCELLANEOUS  MATERIALS  S49 

zinc-lead  whites.  This  mixture  can  be  carried  to  an  unde- 
sirable excess,  for  the  zinc  paint  pulls  and  spreads  poorly 
in  cool  weather.  Practical  painters  agree  that  not  over 
one  third  of  such  a  white  should  be  zinc  oxide.  Further 
adulteration  has  been  practiced  by  using  the  cheaper  benzine 
in  place  of  turpentine  and  rosin  in  the  place  of  drier.  Paints 
made  from  such  materials  fail  to  penetrate  and  soon  crack 
or  peel.  The  Experiment  Station  of  North  Dakota  has 
taken  the  lead  in  the  attempt  to  regulate  the  sale  of  ready 
mixed  paints  by  state  laws.  By  these  laws  the  manufac- 
turer is  required  to  supply  to  the  public  products  of  guaran- 
teed  composition. 

Varnish  of  the  highest  grade  is  made  from  fossil  pro- 
ducts of  tree  resins.  Gum  copal  of  Zanzibar  is  such  a  mate- 
rial. These  resins  are  boiled  with  linseed  oil  and  thinned 
with  turpentine.  Rosin,  a  mixture  of  fresh  resins,  is  an 
inferior  substitute.  Shellac  is  prepared  by  melting  these 
gums  and  allowing  the  liquid  to  cool  and  harden  in  thin 
sheets.     It  is  pared  into  scales  and  dissolved  in  alcohol. 

Would  you  think  the  use  of  benzine  or  turpentine  advis- 
able for  cleaning  paint  and  varnish?  Is  it  not  readily  seen 
that  the  oil  and  resin  solvents  used  to  apply  these  materials 
will  also  either  deface  or  remove  them?  The  safest  cleanser 
for  interior  painted  or  varnished  surfaces  is  a  high-grade, 
practically  neutral  soap,  such  as  Ivory  soap,  applied  with 
water  and  a  soft  chamois  skin.  If  crude,  alkaline  soaps 
or  ammonia  be  used  there  is  danger  of  dissolving  the  surface 
of  varnish  and  deadening  its  luster. 

Pure  soap  solution  cleanses  in  two  ways.  It  emulsifies 
the  fat  or  grease,  that  is,  it  takes  it  into  supension  as  mi- 
croscopic droplets,  as  it  exists  in  milk.  It  also  dissolves 
the  fat  or  grease  by  its  weak  alkalinity. 

Cements  and  mortars  are  widely  used  in  daily  life.  By 
a  few  minutes  thought  you  can  state  many  ways  in  which 
they  are  of  service.  ,  Cement  is  mostly  basic  calcium  silicate. 


350  CHEMISTRY  OF  THE  FARM  AND  HOME 

Natural  cement  rocks  were  discovered  about  1800  at  Louis- 
ville, Kentucky,  and  in  other  parts  of  our  country.  These 
rocks  contain  such  proportions  of  calcium,  aluminium  and 
silicon  as  when  heated  produce  a  material  which  sets  when 
wet.  Portland  cement  was  patented  in  1827  by  a  brick 
maker  living  near  Portland,  England.  It  has  practically 
put  the  natural  cements  out  of  use,  because  it  is  more  uni- 
form in  composition  and  more  dependable.  The  product 
is  made  by  heating  lime  and  clay  in  a  special  furnace.  With 
both  Portland  and  natural  cements  the  material  is  heated 
until  fusion  begins.  The  chemical  reactions  are  left  incom- 
pleted; but  they  are  the  more  complete  the  finer  the  state 
of  the  materials  used.  They  are  also  made  more  complete 
by  thoroughly  mixing  the  materials  with  a  little  water,  and 
by  heating  to  as  high  a  temperature  as  possible.  The 
fused  product,  called  clinker,  consists  of  crystal  masses 
cemented  together  by  an  uncrystalline  material.  The 
crystalline  mass  is  not  a  pure  compound;  but  it  always 
contains  silica  and  lime  in  proportions  of  about  25  per  cent 
and  67  per  cent  respectively.  It  also  contains  about  35 
per  cent  of  ferric  and  aluminium  oxides.  The  cementing 
part  contains  more  aluminium,  less  calcium  and  much  less 
silicon  than  the  crystalline  part.  In  manufacturing  cement 
the  kilns  are  gradually  heated  to  about  1400°  C.  The 
material  first  dries.  Then,  at  just  above  800°  C,  the 
organic  matter  and  carbon  dioxide  are  lost.  Finally,  as 
fusion  begins,  the  lime  combines  with  silica  and  with  alumina 
to  form  salts  new  to  the  mixture.  The  chief  aluminium 
compound  formed  is  tricalcium  aluminate.  This  contains  one 
molecule  of  alumina  or  aluminium  oxide,  acting  as  an  acid, 
combined  with  three  molecules  of  lime,  or  calcium  oxide. 
The  first  setting  of  cement  is  due  to  this  compound,  which 
combines  with  eight  to  twelve  per  cent  of  water.  Later 
in  the  setting  process  the  calciiim  silicates  are  decomposed 
by  water  and  some  calcium  hydroxide  is  set  free.    The 


MISCELLANEOUS  MATERIALS 


351 


silicic  acid  also,  when  set  free,  forms  a  jelly-like  coat  around 
the  particles  of  cement.  No  water  can  penetrate  this  coat, 
and  the  free  water  in  each  such  particle  for  reactions  inside  it 
causes  the  hardening  and  setting  of  the  mass  even  under 
water. 

Concrete  is  used  in  place  of  cement  for  rough  work  on 
a  large  scale,  such  as  piers  and  walls.     Historic  Roman 


^HRMpp^M 

Figure  107.     Splendid  barns  and  silos  built  with  concrete.   They  are  long  lived 
and  almost  wholly  fireproof. — (Courtesy  Universal  Portland  Cement  Co.) 


buildings  were  constructed  from  concrete,  the  use  of  which 
dates  from  ancient  times.  It  consists  of  rock  or  cement 
fragments  bound  together  by  cement.  The  binding  effect 
is  the  more  complete  the  more  complete  the  contact  of  the 
fragments  and  cement.  How  would  you  explain  the  supe- 
riority of  rough  over  smooth  fragments?  Compactness 
is  an  important  quality  in  finished  concrete.  Porous 
material  is  subject  to  accumulation  of  water  and  the  spHt- 
ting  action  of  freezing.  For  this  reason  very  coarse  rock 
fragments  are  to  be  avoided.  Some  of  the  salts  in  sea  water 
tend  to  react  very  slowly  with  the  compounds  of  cement; 


352      CHEMISTRY  OF  THE  FARM  AND  HOME 

and  carbonated  water  dissolves  calcium  from  it  gradually. 
These  agents  do  little  harm,  however.  Where  sewage  is 
exposed  to  the  air  in  contact  with  concrete  it  sometimes 
rapidly  destroys  the  latter.  This  is  due  to  the  formation 
of  sulphuric  acid  by  oxidation  of  hydrogen  sulphide  and  the 
solvent  action  of  the  acid  on  the  binding  compounds  of  the 
cement.  Silage  does  not  dissolve  cement  to  any  extent, 
as  is  sometimes  thought.  With  all  these  materials,  however, 
there  may  be  spreading  force  exerted  by  the  formation  of 
salt  crystals  in  the  cavities  of  the  cement.  Both  physical 
and  chemical  destruction  are,  therefore,  reduced  by  making 
a  uniform,   compact  product. 

Mortar  has  been  used  from  very  ancient  times.  The 
Romans  made  excellent  mortar,  often  using  sand  and 
clay  in  preparing  it.  Plain  mortar  is  calcium  hydroxide, 
made  by  slaking  quicklime  or  calcium  oxide  with  water. 
Sometimes  hair  and  sand  are  mixed  with  it.  Sand  imparts 
strength,  serving  about  like  the  rock  in  concrete.  Hair 
gives  a  body  to  the  mass  which  makes  it  spread  better  and 
helps  hold  it  together  while  drying.  The  chief  process 
causing  setting  of  mortar  is  drying.  While  the  mass  is  still 
moist  the  calcium  hydroxide  may  react  with  carbon  dioxide 
of  the  air.  What  compound  would  be  produced  in  this 
way?  The  process  forms  a  protective  coat  at  the  surface 
of  the  mortar  and  the  carbon  dioxide  does  not  penetrate 
far.  Even  in  Roman  mortars  twenty  centuries  old  only 
the  surface  layer  was  found  to  contain  calcium  carbonate. 

Plaster  is  prepared  from  gypsum,  calcium  sulphate  com- 
bined with  two  molecules  of  water.  That  used  in  building 
the  great  pyramids  of  Egypt  was  made  from  impure  gypsum. 
In  1765  the  great  French  chemist  Lavoisier  discovered  the 
chemical  changes  of  plaster  making.  He  found  that  by  heat- 
ing to  130°  C.  three  molecules  of  water  are  lost  from  two 
molecules  of  gypsum.  The  product  unites  with  water  and 
sets,  when  the  two  are  mixed.     It  is  commonly  known  as 


MISCELLANEOUS  MATERIALS  353 

Plaster  of  Paris,  a  material  much  used  for  molds,  casts 
and  decorative  work.  If  the  gypsum  is  heated  above  194° 
C,  it  loses  all  its  water  and  ''dead  burns."  In  this  condi- 
tion it  is  so  insoluble  that  it  no  longer  sets  when  mixed  with 
water.  Plaster  should  be  mixed  sparingly  with  water. 
By  this  treatment  the  hydrated  salt  crystalizes  from  a 
saturated  solution,  and  forms  interlocking,  radiate  bundles 
of  crystals.  How  would  you  expect  this  interlocking  con- 
dition to  affect  the  strength  of  the  product?  If  the  gypsum 
is  slowly  and  indirectly  heated  to  about  500°  C.  by  the 
gases  from  the  fuels,  it  does  not  ''dead  burn.'*  Its  water 
is  driven  off,  but  the  product  is  soluble  enough  to  set  slowly 
when  mixed  with  water.  It  produces  the  hard  plaster  of 
floorings.  When  mixed  with  mortar,  this  kind  of  plaster 
retards  its  setting  and  hardens  it.  Gelatin  and  starch  paste, 
which  have  affinity  for  water,  are  sometimes  mixed  with 
plaster  to  delay  setting  and  prolong  the  time  during  which 
it  can  be  applied.     Can  you  see  how  they  act? 

Insecticides  are  man's  weapons  in  warfare  against  de- 
structive insect  parasites  of  plants.  These  parasites  so 
sap  and  weaken  the  host  plants  as  to  decrease  or  ruin  crops. 
Among  them  are  included  the  potato  bug,  cabbage  worm 
and  many  other  destructive  pests.  To  combat  these  dif- 
ferent kinds  of  insects  different  methods  must  be  used. 
Those  which  eat  the  foliage  can  be  killed  by  poisoning  the 
surface  of  the  plants.  If  they  are  sucking  insects,  such  as 
plant  lice  and  some  beetles  they  must  be  treated  through 
their  breathing  pores  or  tracheae.  These  open  along  the 
sides  of  the  abdomen.  They  may  be  closed  by  some  sub- 
stance which  will  spread  over  the  surface  of  the  body.  Such 
insects  may  also  be  killed  by  some  gaseous  poison  which 
can  enter  the  tracheae.  Still  another  kind  of  insect,  which 
is  protected  by  a  scale,  can  be  killed  only  by  a  gaseous 
poison,  or  better,  by  some  caustic  substance  which  will 
loosen  the  scale  from  the  tree. 

—23  ' 


t?54  CHEMISTRY  OF  THE  FARM  AND  HOME 

The  standard  remedies  for  all  those  insects  whose  worms 
or  larvae  eat  foliage  are  compounds  of  arsenic.  White 
arsenic  or  arsenious  oxide  is  the  most  common  compound 
of  arsenic.  It  contains  two  atoms  of  the  element  arsenic 
combined  with  three  atoms  of  oxygen.  Dissolved  in  water 
it  is  a  weak  acid  and  combines  with  alkalies  and  metals  to 


■i  4 

^gl^l^.^^^^l^ ' 

•^ ... 

SCABBED                 WORMT   .    f 

^^ 

Hill 

1    mm  '  •♦'■Is 

SCABBED         DEFORMEoi 

^[  "»• 

. 

Figure  108.  The  good  results  from  using  insecticides  and  fungicides.  The  lower 
apples  came  from  a  tree  sprayed  with  a  mixture  of  lime-sulphur  wash  and  lead 
arsenate.     The  tree  yielding  the  upper  apples  was  unsprayed. 

form  salts  called  arsenites.  It  combines  with  two  more 
atoms  of  oxygen  to  form  arsenic  oxide,  which  forms  salts 
called  arsenates.  Sodium  forms  soluble  salts  with  the 
oxides  of  arsenic,  while  calcium  and  some  of  the  common 
metals  such  as  lead  form  insoluble  compounds.  Which  of 
these  kinds  of  salts  would  you  expect  to  give  the  greater 
service?  It  has  been  found  that  only  very  insoluble  com- 
pounds of  arsenic  can  be  used  without  danger  of  killing 
the  plants. 

Paris  green  was  first  used  in  our  western  states  about 
1860.  It  was  appUed  against  the  potato  bug,  for  which  it  is 
still  the  leading  remedy.  For  several  years  it  gave  uncer- 
tain results,  sometimes  killing  the  plants.     The  trouble  has 


MISCELLANEOUS  MATERIALS  355 

been  found  to  be  due  to  soluble  arsenic  compounds.  It 
can  be  prevented  by  adding  an  excess  of  lime  water  to  the 
green  before  applying  it.  Paris  green  is  made  by  boiling 
a  solution  of  copper  acetate  with  a  solution  of  sodium 
arsenite.  It  is  an  insoluble  salt  of  copper  with  both  arsen- 
ious  and  acetic  acids.  By  suspending  it  in  water  it  can 
be  sprayed  upon  foliage.  When  improperly  made  some 
soluble  arsenic  compounds  may  be  present.  These  are 
liable  to  penetrate  and  kill  the  leaves.  When  an  excess 
of  lime  is  added,  it  reacts  with  them  to  form  calcium  arsen- 
ite, and  prevents  the  injury.  Pure  Paris  green  contains 
almost  60  per  cent  of  arsenious  oxide.  On  account  of  the 
danger  from  soluble  arsenic  some  states  have  limited  by  law 
the  amount  of  soluble  arsenious  oxide  permissible  in  this 
insecticide.     Wisconsin  allows  the  presence  of  3.5  per  cent. 

Calcium  arsenite  is,  as  you  may  glean  from  the  pre- 
ceding paragraph,  a  safe  insecticide.  From  what  has  pre- 
ceded you  can  readily  see  how  it  is  made.  It  is  an  insoluble 
compound  which  does  not  inj  ure  the  leaf,  but  when  consumed 
by  insects  it  is  made  soluble  and  poisonous  by  their  digestive 
fluids.  This  is  the  chief  constituent  of  London  purple, 
a  waste  product  of  the  dye  industry,  formerly  much  used 
as  an  insecticide.     Zinc  arsenite  is  also  an  insecticide. 

Lead  arsenate  is  prepared  by  adding  lead  acetate  to 
sodium  arsenate.  It  is  sold  in  the  form  of  a  paste  ready 
to  be  suspended  in  water  for  spraying.  Dry  lead  arsenate 
is  of  little  use  as  it  does  not  remain  suspended  well.  This 
causes  uneven  application  to  the  foliage  and  clogging  of  the 
spray  nozzles.  Lead  hydrogen  arsenate,  or  acid  lead  ar- 
senate, is  formed  when  some  lead  salts  are  added  to  sodium 
arsenate.     This  contains  more  arsenic  than  the  natural  salt. 

Lime-sulphur  wash  is  useful  against  insects  with  pro- 
tective covering  such  as  the  San  Jose  scale  of  fruit  trees. 
It  is  prepared  by  boiling  sulphur  with  lime  in  the  propor- 
tion of  1  pound  of  each  to  2.5  gallons  of  water.     For  con- 


356 


CHEMIFiTRY  OF  THE  FARM  AND  HOME 


venience,  large  amounts  of  the  wash  are  prepared  in  elevated 
casks  by  passing  live  steam  through  the  water.  The  wash 
is  then  diluted  to  the  desired  strength  and  siphoned  off  for 
spraying.  As  the  wash  is  boiled  it  passes  through  deeper 
shades  of  yellow  to  an  orange  color.  At  the  same  time 
the  calcium  combines  with  the  sulphur  in  several  proportions. 
The  compounds  produced  are  called  polysulphides.     Cal- 


Figure  109.  An  economical  outfit  for  preparing  lime-sulphur  wash.  It 
includes  a  pump,  for  drawing  water  to  the  platform,  scales  for  weigh- 
ing the  lime  and  sulphur  and  a  steam  boiler  for  heating  the  wash. 


cium  pentasulphide,  the  last  of  these,  contains  one  atom  of 
calcium  and  five  atoms  of  sulphur.  Only  the  use  of  the 
most  finely  divided  form  of  sulphur,  the  "flowers,"  insures 
that  the  desired  chemical  reactions  will  occur.  Impure 
lime  containing  magnesium  produces  reactions  in  which 
hydrogen  sulphide  is  set  free,  and  must  be  avoided.  Sul- 
phur wash  acts  first  as  a  solvent  upon  the  scale  insects, 
loosening  them  from  the  tree.  The  scales  consist  of  chitin, 
a  hard  protein  substance  related  to  hair  and  horn.  These 
compounds  are  acted  upon  and  made  soluble  by  alkaHes, 


MISCELLANEOUS  MATERIALS  357 

and  the  sulphides  of  the  wash  are  alkaline.  Then  the 
sulphides  which  penetrate  to  the  insect  are  oxidized  by  the 
air  to  calcium  sulphate  and  free  sulphur.  These  chemical 
changes  and  their  products  kill  the  insect. 

Petroleum  oils  related  to  kerosene  and  parafiine  are 
useful  for  destroying  most  sucking  insects.  These  insects 
cannot  be  poisoned,  since  they  feed  only  on  the  sap  of 
the  plant.  The  oils  form  a  film  over  their  bodies  and 
suffocate  them.  Oils  cannot  be  applied  undiluted,  nor 
can  they  be  diluted,  as  you  know,  with  water.  Strong 
soap  solutions,  however,  form  emulsions  with  them.  You 
will  recall  the  nature  of  an  emulsion  from  your  study  of 
milk  fat.  These  preparations  are  called  miscible  oils.  To 
prepare  them,  fish  oil  is  boiled  with  strongest  potassium 
hydroxide  solution,  in  the  proportion  of  one  gallon  to  one 
and  a  half  gallons  respectively.  Carbolic  acid,  kerosene 
and  water  are  added  in  small  amounts.  This  makes  the 
soap  solution.  Why  will  not  a  sodium  soap  serve  for  this 
purpose?  While  the  soap  solution  is  still  hot  the  paraffine 
oil  is  stirred  in.  This  should  be  added  in  the  proportion 
of  about  ten  gallons  of  oil  to  one  gallon  of  soap  solution. 
This  makes  the  miscible  oil,  which  can  be  diluted  as  desired, 
with  from  twelve  to  fifteen  times  its  volume  of  water,  for 
the  final  spray  fluid. 

Hydrocyanic  acid,  commonly  called  Prussic  acid,  is  a 
powerful  gaseous  poison.  It  is  formed  by  adding  potassium 
cyanide  to  an  excess  of  strong  sulphuric  acid.  It  is  especially 
useful  for  killing  insects  in  crowded  greenhouses.  It  is 
also  useful  against  vermin  in  dwellings.  Scale  insects  on 
small  fruit  stock  may  be  treated  in  closed  buildings.  Lar- 
ger trees  are  inclosed  in  tents  for  treatment.  In  all  these 
cases  the  space  to  be  treated  is  measured  and  one  ounce 
of  pure  potassium  cyanide  is  used  per  100  cubic  feet.  To 
avoid  danger  the  building  should  be  opened  and  ventilated 
before  entering  after  fumigation. 


358  CHEMISTRY  OF  THE  FARM  AND  HOME 

Carbon  bisulphide  is  very  useful  against  grain  weevils. 
It  is  a  colorless,  volatile  liquid  containing  one  atom  of  carbon 
to  two  atoms  of  sulphur.  When  placed  in  open  dishes  at 
the  surface  of  the  grain  its  heavy  vapors  sink,  and  should 
be  allowed  to  escape  at  the  bottom  of  the  bin. 

Fungicides  are  materials  used  to  kill  parasites  upon 
plants.  To  kill  them  without  injuring  the  host  is  a  delicate 
task.  Many  plant  diseases,  such  as  the  rusts  and  blights, 
are  due  to  plants  of  microscopic  size  belonging  to  the  same 
great  group  as  the  mushrooms.  These  parasites  enter  the 
soft  tissue  of  the  host,  frequently  through  the  stomata  of 
the  leaves,  and  deprive  it  of  food.  They  thus  weaken  or 
even  kill  the  host  crops.  It  is  difficult  to  apply  poison  to 
them  without  danger  that'  it  will  enter  and  inj  ure  the  host. 

Sulphur  and  some  of  its  compounds  were  used  as  fungi- 
cides as  early  as  1880.  They  have  been  used  a  great  deal  to 
suppress  mildew  in  greenhouses.  Potassium  sulphide  is 
esteemed  for  the  purpose,  sprayed  in  a  solution  of  6  per  cent 
strength.  The  base  is  so  strong  and  the  acid  so  weak  in 
this  salt  that  stronger  solutions  are  so  alkaline  as  to  kill 
the  plants.  A  modern  preparation  of  sulphur  set  free  from 
its  compounds  by  chemical  reaction  is  very  effective.  It 
is  an  extremely  finely  divided  material  known  as  ''atomic 
sulphur,"  which  is  suspended  in  water  for  spraying. 

Copper,  in  the  form  of  some  of  its  compounds,  has  been 
the  standard  fungicidal  agent  for  a  long  time.  Copper 
sulphate  solution  is  too  acid  for  use.  Copper  ammonium 
carbonate  solution,  made  by  dissolving  copper  carbonate 
in  a  slight  excess  of  ammonia,  is  sometimes  used  as  a  fungi- 
cide. Bordeaux  mixture  has  been  the  leading  fungicide 
since  about  1880.  It  is  a  suspension  in  water  of  insoluble 
mixed  compounds  of  copper  and  calcium  with  sulphuric 
acid.  These  compounds  are  formed  as  a  precipitate  when 
copper  sulphate  solution  is  added  to  limewater.  In  order 
to  insure  that  it  will  remain  suspended  well  when  mixed 


MISCELLANEOUS  MATERIALS 


359 


11 

/  2  3 


with  water  it  must  be  precipitated  in  the  finest  particles 
possible.  This  result  is  accomplished  by  dissolving  the 
lime  and  copper  sulphate  each  in  one  half  the  volume  of 
water  to  be  used.  After  the  lime  water  is  cold  the  two 
solutions  are  poured  at  the  same  time 
into  a  mixing  barrel.  They  must  be 
poured  slowly  with  constant  stirring. 
The  proportions  used  are  3.5  pounds  of 
pure  Hme  to  10  pounds  of  copper  sul- 
phate in  50  gallons  of  water.  Unless 
an  excess  of  lime  is  present,  the  mix- 
ture is  Hable  to  contain  enough  soluble 
copper  to  injure  the  fohage.  This  is 
liable  to  be  the  case,  if  only  impure 
lime  can  be  had.  To  avoid  this  trouble, 
a  little  of  the  mixture  is  filtered  and 
tested  by  adding  a  few  drops  each  of 
acetic  acid  and  potassium  ferrocyanide 
solution.  If  soluble  copper  is  present 
the  liquid  turns  brown  as  a  result  of 
the  presence  of  copper  ferrocyanide. 
More  lime  water  is  added  until  the  mix- 
ture no  longer  gives  this  test.  When 
Bordeaux  mixture  is  appHed  to  foliage, 
the  copper  gradually  becomes  soluble, 
chiefly  by  the  action  of  carbonic  acid. 
This  reagent  is  formed  from  carbon 
dioxide  which,  as  you  will  recall,  is  a 
product  of  the  respiration  of  the  leaf. 
These  changes  are  usually  sufficient  to 
kill  the  parasitic  fungi  without  injuring 
the  host  plants.  Bordeaux  mixture  de- 
rives its  name  from  the  province  of  France  where  the  fav- 
orable effects  of  lime  and  copper  salts  together  upon  grapes 
was  first  observed. 


Figure  110.  Bordeaux 
mixture  properly  and 
improperly  made.  1 
and  2  were  photo- 
graphed 3  H  hours 
after  preparation.  3 
was  photographed  15 
minutes  after  prepar- 
ation. In  1  the  lime 
solution  was  first 
cooled  and  then  pour- 
ed simultaneously  with 
the  copper  sulphate 
solution  into  a  mixing 
vessel.  In  2  the  so- 
lutions were  mixed 
while  the  limewater 
was  hot.  In  3  one 
solution  was  poured 
into  the  other  while 
the  limewater  was 
hot.  It  is  desirable 
to  have  the  Bordeaux 
mixture  remain  sus- 
pended as  long  as  pos- 
sible. 


360  CHEMISTRY  OF  THE  FARM  AND  HOME 

Disinfectants  are  frequently  necessary  materials  in  the 
home  or  stable.  They  may  be  used  either  to  rid  rooms 
of  bacteria  causing  infectious  diseases  or  to  render  decaying 
and  fecal  matter  less  objectionable. 

Carbolic  acid  and  related  coal  tar  compounds  are  com- 
monly used  for  this  purpose.  At  ordinary  temperatures  car- 
bolic acid  is  crystalline,  but  it  becomes  liquid  by  heating 
gently.  The  liquid  can  be  mixed  with  solid  matter.  For 
spraying  surfaces  it  is  dissolved  in  water  to  a  solution  of 
about  five  per  cent  strength. 

Formaldehyde  is  a  powerful  disinfectant.  It  is  a  gas 
produced  by  oxidation  from  methyl  alcohol  or  "wood  alco- 
hol." One  can  obtain  it  from  the  pharmacist  as  formaUn, 
a  40  per  cent  solution  of  formaldehyde  in  water.  This  can  be 
diluted  to  any  desired  strength  for  spraying.  In  disinfect- 
ing rooms  the  formaldehyde  is  forced  in  from  the  outside. 
The  rooms  are  then  aired. 

Mercury  bichloride,  or  corrosive  sublimate,  is  a  powerful 
disinfectant  and  poison.  It  is  a  salt  formed  by  the  union 
of  one  atom  of  mercury  with  two  atoms  of  chlorine.  A  0.1 
to  0.2  per  cent  solution  of  this  salt  is  very  commonly  used 
as  a  disinfectant  wash  applied  to  the  human  body.  Much 
stronger  solutions  are  used  as  sprays  and  mixed  with  material 
to  be  disinfected. 

These  three  disinfectants  are  all  extremely  poisonous  to 
animals,  as  well  as  to  bacteria,  and  must  be  used  only  with 
great  care  and  judgment.  Accidental  deaths  of  human 
beings  from  taking  carbolic  acid  or  corrosive  sublimate 
internally  are  too  common. 

Calcium  hypochlorite,  or  "bleaching  powder,"  is  a  rather 
mild  and  favorite  disinfectant.  It  contains  one  atom  each 
of  calcium  and  oxygen  combined  with  two  atoms  of  chlo- 
rine. Frequently  it  is  wrongly  called  "chloride  of  lime." 
It  is  a  white  powder  which  gives  off  chlorine  gradually. 
This  chlorine  decomposes  water,  forming  hydrochloric  acid 


,r MISCELLANEOUS  MATERIALS  361 

and  releasing  oxygen.  The  latter  acts  as  a  disinfectant  by 
oxidizing  the  organic  matter  of  bacteria.  In  the  same 
manner  it  acts  as  a  bleaching  agent  by  oxidizing  colored  to 
colorless  compounds.  Would  you  expect  bleaching  powder 
to  disinfect  perfectly  dry  material? 

Hydrogen  peroxide,  consisting  of  two  parts  each  of  hy- 
drogen and  oxygen,  also  acts  as  a  bleaching  and  disinfect- 
ing agent  by  releasing  oxygen.  As  commonly  sold  it  is  a 
four  per  cent  solution  in  water,  with  some  preserving 
agent  added. 

SUMMARY 

Among  the  multitude  of  materials  useful  in  daily  life  there  is  none 
free  from  dependence  upon  chemical  properties  or  reactions  for  its  value. 
Clothing  fabrics  are  made  from  plant  and  animal  fibers,  which  are 
carbohydrate  and  protein  compounds  respectively.  Differences  in 
chemical  properties  cause  the  animal  fibers  to  take  up  dyes  more  read- 
ily than  the  plant  fibers.  The  latter  generally  require  the  use  of  some 
mordant  deposited  in  the  fiber,  which  increases  their  affinity  for  the 
dye.  Cleansers  and  stain  removers  act  generally  as  solvents  for  com- 
pounds soiling  clothing  fabrics,  while  bleaching  agents  act  by  oxidation. 
Care  is  necessary  that  these  materials  may  not  remove  the  dye  from 
the  fabric. 

Paints  of  highest  grade  are  pigments  of  metallic  compounds 
mixed  with  linseed  oil  and  thinned  with  turpentine.  The  turpentine 
acts  as  a  solvent,  carrying  the  pigment  into  wood,  and  the  oil  dries 
and  "sets"  the  paint  by  oxidizing.  Varnishes  are  plant  gums  and 
resins  dissolved  in  linseed  oil.  Any  fat  solvent  must  be  avoided  in 
cleaning  painted  or  varnished  surfaces. 

Mortar,  plaster  and  cement  are  compounds  of  calcium.  The  first 
is  made  from  quickhme  and  the  second  from  partly  dehydrated  gyp- 
sum .  Both  compounds  combine  with  water  when  made  up,  and  the 
free  water  left  dries  out.  Cement  is  made  by  heating  a  mixture  of 
lime  and  clay  very  hot.  Its  chief  compounds  are  salts  containing  cal- 
ciunoi  combined  with  silicon  and  with  aluminium  as  acid-forming 
elements.  Calcium  aluminate  "sets"  by  combining  with  water,  while 
the  silicates  are  decomposed  and  so  protect  the  cement  particles  that 
setting  proceeds  even  under  water. 

Insecticides  and  fungicides  are  mostly  practically  insoluble  com- 
pounds which  are  suspended  in  water  and  sprayed  upon  crops  to  kill 
parasites  without  injuring  the  host  plants.    Arsenic  compounds  are 


362  CHEMISTRY  OF  THE  FARM  AND  HOME 

applied  to  insects  and  copper  compounds  to  plant  parasites.  Insects 
not  reached  by  poisons  at  the  surface  of  the  foilage  are  either  suffocated 
by  paraffine  oils,  sprayed  as  emulsions  in  soap  solution,  or  loosened  from 
the  plant  and  poisoned  by  sulphides  of  calcium.  The  insoluble  poison- 
ous c?mpounds  are  made  gradually  soluble  by  solvents  within  the  in- 
sect and  on  the  surface  of  the  foliage.  Disinfectants  kill  bacteria  by 
acting  either  as  poisons  or  as  oxidizing  agents.  They  are  mostly  power- 
ful poisons  requiring  careful  usage. 

QUESTIONS 

1.  What  is  the  composition  of  cotton  fiber?  Why  is  it  well 
suited  for  spinning?  What  condition  is  necessary  for  spinning  quality? 

2.  How  is  mercerized  cotton  prepared? 

3.  How  is  artificial  silk  made? 

4.  What  are  the  changes  of  retting? 

5.  What  is  the  composition  of  hemp  fiber? 

6.  How  is  wool  cleaned?  What  is  the  structure  of  its  fiber? 
What  is  its  composition? 

7.  What  is  the  source  of  silk  fiber?    What  is  its  composition? 

8.  What  is  the  source  of  modern  dyes? 

9.  What  is  a  direct  dye?    A  substantive  dye?     A  mordant? 

10.  What  is  meant  by  dry  cleaning? 

11.  How  you  would  remove  paint  or  pitch  stains?  Ink  stains? 
Rust  spots?    Grass  stains?    Blood  stains?     Fruit  stains? 

12.  How  can  cloth  be  bleached? 

13.  What  is  lead  white? 

14.  What  are  "driers"? 

15.  What  is  the  composition  of  paints  for  metal  surfaces? 

16.  How  is  varnish  made? 

17.  How  should  painted  or  varnished  surfaces  be  cleaned? 

18.  How  is  Portland  cement  made?     What  is  its  composition? 

19.  What  are  the  chemical  processes  of  setting  of  cement? 

20.  What  is  the  composition  of  mortar? 

21.  What  are  the  chemical  changes  in  the  making  and  setting 
of  plaster? 

22.  State  three  ways  in  which  insecticides  act. 

23.  What  is  the  composition  of  Paris  Green? 

24.  How  is  lead  arsenate  prepared? 

25.  What  is  the  objection  to  soluble  compounds  of  arsenic  in 
insecticides?  How  can  their  presence  be  prevented?  What  chemical 
change  does  it  undergo  on  foHage? 

26.  What  is  a  miscible  oil?     For  what  is  it  used? 

27.  Name  two  gaseous  insecticides. 

28.  What  is  a  fungicide? 

29.  How  should  Bordeaux  mixture  be  prepared?  Why  should 
an  excess  of  copper  be  avoided?     How  can  it  be  corrected? 

30.  What  is  the  purpose  of  using  disinfectants? 

31.  Name  three  important  disinfectants,  stating  the  chemical 
nature  of  each? 


EXPERIMENTS 


CHAPTER  I. 
EXPERIMENT  1 

Object: — To  study  the  properties  of  elements,  compounds,  and 
mixtures. 

Apparatus  and  Material: — Magnifying  glass,  magnet,  test  tubes, 
finely  powdered  iron,  powdered  sulphur,  and  dilute  hydrochloric  acid. 

Method: — Part  A.  Secure  some  finely  powdered  iron  and  sulphur. 
Subject  each  of  them  separately  to  the  following  tests:  (a)  Note  their 
color,  odor,  etc.  (b)  Examine  with  a  small  magnifying  glass,  noting 
the  crystalline  form,  (c)  Test  with  a  magnet,  (d)  Place  a  small  quan- 
tity in  a  test  tube  and  add  5  c.  c.  of  dilute  hydrochloric  acid. 

Part  B.  Stir  together  3  grams  of  the  sulphur  and  5  grams  of  the 
iron.     Test  the  mixture  in  the  four  ways  directed  above. 

Part  C.  Stir  together  a  fresh  portion  of  3  grams  of  sulphur  and  5 
grams  of  iron.  Place  the  mixture  in  a  6  inch  test  tube.  Heat  with  a 
small  flame.  When  the  mass  glows  Hke  a  red  hot  coal,  remove  the  tube 
from  the  flame.  When  the  action  is  over,  plunge  the  tube  into  some 
cold  water  in  a  beaker.  Carefully  pick  out  the  fused  mass  from  the 
broken  glass,  dry,  and  powder  it.  Test  in  the  four  ways  indicated 
above. 

Results: — What  is  the  appearance  of  the  sulphur  in  the  first  two 
cases?  Is  any  sulphur  visible  after  the  mixture  has  been  heated? 
What  is  the  effect  of  the  magnet  in  the  three  parts  of  the  experiment? 
Of  the  hydrochloric  acid?  Does  the  iron  still  exist  as  such  in  parts  B 
and  C?  Does  the  sulphur  still  exist  as  such  in  parts  B  and  C?  Is  it 
easier  to  separate  sulphur  and  iron  when  they  are  in  a  mixture  before 
or  after  heating? 

EXPERIMENT  2 

Object: — To   study  examples   of   physical   change. 

Apparatus  and  Material: — Balance  and  weights,  porcelain  evap- 
orating dish,  water  bath,  magnifying  glass,  porcelain  crucible,  test 
tubes,  funnel,  sugar,  iodine,  alcohol,  potassium  iodide  solution. 

Method:— Part  A.  Weigh  5  grams  of  sugar,  add  to  25  c.  c.  of 
water,  and  stir  until  dissolved.  Place  the  solution  in  a  porcelain 
evaporating  dish  and  evaporate  to  dryness  upon  a  water  bath.     Take  a 

363  I 


364  CHEMISTRY  OF  THE  FARM  AND  HOME 

small  amount  of  the  original  sugar  and  also  of  the  solid  residue  in  the 
evaporating  dish.  Apply  the  following  tests  to  them: Taste  a  portion, 
examine  some  with  a  magnifying  glass,  heat  a  httle  in  a  porcelain 
crucible. 

Results: — Describe  the  results  of  these  tests.  Is  there  any  dif- 
ference between  the  two  samples?  Does  the  process  of  solution  seem 
to  have  any  effect  upon  the  properties  of  the  sugar? 

Part  B.  Place  a  very  small  piece  of  iodine  in  a  test  tube.  Heat 
the  bottom  of  the  tube  gently  in  a  flame  and  pass  the  vapors  upon  a 
cold  surface,  as  the  interior  of  a  porcelain  dish  or  an  inverted  funnel. 
Study  both  the  original  and  the  condensed  (sublimed)  materials.  What 
is  their  color  and  general  appearance?  WTiat  is  the  effect  of  heat  upon 
them?    Are  they  soluble  in  a  solution  of  potassium  iodide  or  alcohol? 

Results: — Is  there  any  difference  between  the  samples?  Does 
the  process  of  heating  affect  the  iodine  in  any  way? 

EXPERIMENT  3 

Object: — To  study  examples   of   chemical   change. 

Apparatus  and  Material: — Test  tubes,  crucible,  crucible  tongs, 
sugar    and    magnesium    ribbon. 

Method: — Part  A.  Place  two  grams  of  sugar  in  a  clean  6  inch 
test  tube.  Hold  the  tube  horizontally  and  heat  slowly  and  carefully 
until  the  sugar  begins  to  darken.  Remove  the  tube  from  the  flame  and 
examine  it  carefully.  Replace  in  the  flame  and  heat  strongly  until 
no  further  change  occurs.     Note  results.     What  products  are  formed? 

Part  B.  Place  2  grams  of  sugar  in  a  small  crucible.  Heat  slowly 
and  carefully,  noting  all  the  results.    Describe  the  changes  which  occur. 

Results: — Is  there  any  difference  between  heating  sugar  in  a  test 
tube  and  in  a  crucible?  If  so,  what  is  the  most  striking  distinction? 
What  is  the  essential  difference  in  these  two  methods? 

Part  C.  Take  a  small  piece  of  magnesium  ribbon  about  1}/^  inches 
long.  Grasp  it  with  a  pair  of  crucible  tongs  or  forceps  and  light  it  in 
the  flame  of  a  burner.     What  is  the  result? 

Results: — State  at  least  two  differences  in  the  properties  of  the 
original  and  the  resulting  materials.  Is  there  any  difference  between 
the  light  produced  in  this  experiment  and  that  from  an  ordinary  elec- 
tric bulb  or  a  kerosene  lamp? 

EXPERIMENT  4 

Object: — To  learn  the  effect  of  heating  a  metal  with  and  with- 
out   air. 

Apparatus  and  Material: — Porcelain  crucible,  stout  iron  wire, 
lead  or  tin  or  solder,  powdered  borax  or  calcined  magnesia. 


EXPERIMENTS  365 

Method: — Part  A.  Plaoe  5  grams  of  lead,  tin,  or  solder  in  a  por- 
celain crucible.  Heat  strongly  until  the  metal  is  melted  and  stir 
continually  with  a  stout  iron  wire.  After  the  mass  has  become  of 
uniform  powdery  texture  throughout  (homogeneous),  allow  the  crucible 
and  its  contents  to  cool. 

Part  B.  Place  another  5  gram  portion  of  the  metal  in  a  second 
crucible  and  cover  the  metal  with  a  rather  deep  layer  of  borax  powder 
or  calcined  magnesia.  Heat  until  the  metal  is  melted  and  stir  for  the 
same  length  of  time  as  required  in  part  A.  Cool  the  crucible  and  re- 
move the  layer  of  magnesia. 

Results: — Examine  the  contents  of  both  crucibles  and  state  the 
results  of  the  experiment.  Is  there  any  marked  difference  in  the  prop- 
erties of  the  two  masses?  What  is  the  reason  for  such  a  difference? 
Which  part  of  the  experiment  illustrates  a  physical  change  and  which 
part  a  chemical  change? 

CHAPTER  n. 

EXPERIMENT  5 

Object: — To  show  the  presence  of  water  in  a  series  of  substances. 

Apparatus  and  Material: — Test  tubes,  uncooked  potato,  uncooked 
meat,   clay  and  copper  sulphate. 

Method: — Place  a  small  amount  of  uncooked  potato,  uncooked 
meat,  clay,  and  copper  sulphate  in  separate  test  tubes.  Heat  the  tube 
containing  the  potato  carefully  in  a  horizontal  position  in  the  flame  of 
the  burner  nearly  to  the  point  of  blackening  the  potato.  Withdraw 
the  tube  from  the  flame  and  examine  the  sides  of  the  tube.  Apply 
the  same  treatment  to  the  other  three  tubes. 

Results: — Is  there  any  evidence  as  to  the  presence  of  water  in  any 
of  the  cases?  State  approximately  the  relative  amounts  of  water 
present  in  each  case,  that  is,  large  or  small.  State  of  what  general 
classes  of  materials  the  examples  chosen  are  typical. 

EXPERIMENT  6 

Object: — To  show  that  water  is  formed  by  the  burning  of  sub- 
stances which  contain  hydrogen. 

Apparatus  and  Material: — Beaker,  candle,  wood. 

Method: — Hold  a  lighted  candle  under  a  glass  full  of  cold  water. 
After  a  minute  or  two,  remove  the  candle  and  examine  the  bottom  of 
the  glass.  If  necessary,  rub  the  forefinger  over  the  glass  to  ascertain 
the  result.  Repeat  the  experiment  by  holding  a  cold  surface  of  glass 
or  metal  over  a  piece  of  burning  wood  or  the  burner  that  is  used  as  a 
source   of   heat   in   the   laboratory. 


366  CHEMISTRY  OF  THE  FARM  AND  HOME 

Results: — What  result  is  common  to  all  of  these  tests?  What 
conclusions  can  be  drawn  as  to  the  burning  of  substances  of  plant 
and  animal  origin? 

EXPERIMENT  7 

Object: — To  study  the  composition  of  natural  waters. 

Apparatus  and  Material:— Water  bath,  evaporating  dish,  several 
samples  of  natural  waters. 

Method: — Three  students  may  work  together  in  this  experiment, 
one  using  rain  water,  another  artesian  well  water,  and  a  third  using 
surface  well  water. 

Fill  a  water  bath  half  full  of  water,  heat  to  boiling,  and  place  an 
evaporating  dish  upon  it.  In  the  evaporating  dish  place  some  of  the 
water  to  be  tested,  and  evaporate  100  c.c.  to  dryness.  Is  there  any 
residue  or  not?  What  is  its  nature?  Moisten  the  end  of  the  httle 
finger,  touch  the  residue,  and  taste  the  material.     Result? 

Dry  the  bottom  of  the  dish,  and  heat  slowly  and  carefully  with 
the  flame.  Is  there  any  change  in  the  appearance  of  the  material? 
Repeat  these  tests  with  each  sample  of  water,  or  the  three  students 
may  compare  notes  upon  their  respective  samples. 

Results: — State  the  two  principal  effects  in  each  case.  State  the 
chief  differences  in  the  character  of  the  samples.  Which  is  the  purer 
of  the  samples  examined? 

Note: — By  careful  work  the  student  may  determine  the  amount 
of  total  sohds  in  water.  Weigh  the  dish  before  and  after  the  water  is 
evaporated.  The  difference  in  weight  is  the  amount  of  soUds  in  the 
water  taken. 

EXPERIMENT  8 

Object: — To  show  whether  water  aids  chemical  reactions. 

Apparatus  and  Material: — Beaker,  glass  rod,  baking  soda,  pow- 
dered tartaric  acid. 

Method: — Place  2  grams  of  baking  soda  and  2  grams  of  powdered 
tartaric  acid  in  a  glass.  Mix  the  two  sohds  intimately  by  stirring 
with  a  glass  rod.  Result?  Add  a  drop  of  water  to  the  mass.  Result? 
Add  more  water  gradually  until  there  is  no  further  action. 

Results: — What  effect  did  water  have  upon  the  chemicals?  Is 
this  reaction  similar  to  that  of  baking  powder?    To  Seidhtz  powders? 

EXPERIMENT  9 

Object: — To  show  the  effect  of  water  upon  the  properties  of 
substances. 

Apparatus  and  Material: — Test  tubes,  crucible,  powdered  copper 
sulphate,  powdered  alum. 


EXPERIMENTS  367 

Method: — Heat  a  small  amount  of  powdered  copper  sulphate 
in  a  test  tube  until  all  the  water  is  driven  off.  Cool.  Compare  the 
appearance  of  the  product  with  that  of  the  original  material.  Add 
a  single  drop  of  water  to  the  residue.     What  is  the  result? 

Heat  a  small  amount  of  powdered  alum  in  a  crucible  until  all 
water  is  driven  off.  Cool,  remove  the  dry  mass,  and  touch  the  sub- 
stance to  the  tongue.  Compare  also  the  taste  of  the  original  material. 
Results? 

Results: — Does  water  change  any  of  the  properties  of  these  two 
substances? 

EXPERIMENT  10 

Object: — To  show  the  effect  of  a  metal,  sodium,  upon  water. 

Apparatus  and  Material: — Large  beaker  or  wide  mouth  bottle, 
glass  plate,  paper,  sodium  metal,  filter  paper,  red  litmus  paper. 

Method: — Part  A.  Place  about  100  c.c.  of  distilled  water  in 
a  large  beaker  or  wide  mouth  bottle.  Take  a  piece  of  sodium  not 
larger  than  a  small  pea  and  drop  it  upon  the  water,  immediately  cov- 
ering the  container  with  a  glass  plate  or  a  piece  of  paper.  Stand 
back  from  the  apparatus  just  far  enough  to  see  the  reaction.  Wait 
for  the  slight  explosion  which  usually  occurs  soon  after  the  action  stops. 
Describe  all  that  has  happened  in  the  experiment. 

Part  B.  Continue  the  experiment.  Place  a  small  piece  of  filter 
paper,  the  size  of  a  quarter,  on  the  surface  of  the  water.  Before  the 
paper  sinks,  carefully  drop  a  small  piece  of  sodium,  the  same  size  as 
used  above,  upon  the  paper.  Cover  the  glass,  stand  back,  and  note 
the  result. 

Results: — Is  there  any  difference  in  the  results  of  the  two  parts 
of  the  experiment?  If  so,  to  what  is  this  due?  What  is  probably  the 
cause  of  the  bright  color  seen  in  part  B?  If  sodium  reacts  so  violently 
with  water,  is  it  a  safe  chemical  to  leave  carelessly  in  the  open  air? 
Why?  How  is  the  metal  protected  from  the  air?  What  other  pur- 
pose is  there  in  protecting  the  metal?  Does  sodium  seem  to  have  any 
effect  upon  the  fingers?     Why? 

Part  C.  Place  a  piece  of  red  litmus  paper  in  the  liquid  from  the 
above  experiments.  Also  cautiously  rub  some  of  the  liquid  between 
the  thumb  and  forefinger.  Again  very  carefully  touch  the  tip  end 
of  the  tongue  to  the  finger  moistened  with  the  liquid.  Repeat  these 
tests  with  distilled    water. 

Results: — State  the  results.  What  is  the  conclusion  in  regard 
to  the  effect  of  sodium  upon  water? 

Caution: — Do  not  handle  sodium  with  wet  hands  or  with  wet 


368  CHEMISTRY  OF  THE  FARM  AND  HOME 

forceps.     Do  not  put  sodium  into  the  waste  jar.     Return  all  extra  pieces 
of  this  metal  to  the  instructor. 

EXPERIMENT  11 

Object: — To  prepare  oxygen. 

Apparatus  and  Material: — 8-inch  hard  glass  test  tube,  pneumatic 
trough,  3  bottles,  crucible,  cardboard,  potassium  chlorate,  manganese 
dioxide. 

Method: — Weigh  10  grams  of  potassium  chlorate  and  10  grams 
of  manganese  dioxide,  mix  thoroughly,  and  place  in  an  8  inch  test 
tube  (preferably  of  hard  glass).  Arrange  the  apparatus  as  shown  in 
Figure  11.  Fill  the  pneumatic  trough  with  water  until  the  shelf  is  just 
covered.  Fill  three  bottles  full  of  water,  cover  each  with  a  small 
glass  plate  or  cardboard,  invert  them  in  the  trough,  and  remove  the 
cover. 

Heat  a  small  amount  of  the  mixture  of  equal  parts  of  chlorate  and 
manganese  dioxide  in  an  open  crucible.  If  there  is  no  explosion  it  is 
safe  to  proceed  with  the  experiment.  Heat  the  test  tube  gently  at 
first,  gradually  increasing  the  temperature  until  there  is  a  steady 
flow  of  gas  issuing  from  the  outlet  of  the  generator.  Then  place  a  bot- 
tle over  the  bubbles  of  gas  and  displace  all  the  water  in  the  bottle  with 
the  gas.  Fill  the  other  two  bottles  with  the  gas  in  the  same  way. 
Now  remove  the  end  of  the  delivery  tube  from  the  water.  Why? 
Also  take  each  bottle  as  it  is  filled  and  cover  with  a  wet  filter  paper. 
Proceed  to  the  next  experiment  immediately. 

EXPERIMENT  12 

Object: — To  demonstrate  the  properties  of  oxygen. 

Apparatus  and  Material: — Piece  of  chalk  hollowed  at  one  end,  pic- 
ture wire,  wood  sphnter,  powdered  sulphur. 

Method: — Part  A.  Into  one  bottle  of  oxygen  prepared  in  the 
previous  experiment  dip  a  glowing  stick  of  wood  or  wax  taper.  Result? 
Remove  the  stick,  extinguish  the  flames  except  a  spark,  and  repeat 
as  many  times  as  possible,  gradually  lowering  the  stick  more  and  more 
into  the  bottle.  What  is  the  effect  of  the  gas  upon  the  glowing  stick? 
Does  the  gas  itself  burn?  What  property  of  oxygen  does  this  illus- 
trate? 

Part  B.  Place  a  small  amount  of  sulphur  in  a  deflagrating  spoon 
or  piece  of  hollowed  chalk.  Hold  in  the  flame  until  the  sulphur  begins 
to  bum,  then  lower  into  the  second  bottle  of  oxygen.  Results?  Is 
there  any  change  in  the  flame?  Describe  it.  Brush  a  little  of  the  gas 
cautiously  toward  the  nose.     What  does  it  smell  like? 


EXPERIMENTS  369 

Part  C.  In  the  third  bottle  place  enough  water  to  cover  the 
bottom.  Take  a  piece  of  picture  wire  6  inches  long  and  unwind  one 
end  of  it.  Dip  this  end  in  melted  sulphur,  and  while  this  is  burning, 
lower  it  into  the  bottle  of  oxygen.  Results?  Why  is  the  iron  tipped 
with  burning  sulphur?  Of  what  use  is  the  water  in  the  bottom  of  the 
bottle? 

Results: — What  do  these  experiments  show  in  regard  to  the  prop- 
erties of  oxygen?  Why  is  combustion  more  active  in  an  atmosphere 
of  the  pure  gas  than  in  the  air? 

EXPERIMENT  13 

Object: — To  study  the  construction  of  the  Bunsen  burner. 

Apparatus  and  Material: — The  Bunsen  burner,  a  piece  of  bright 
iron,  match. 

Method: — Take  the  Bunsen  burner  apart.  Draw  a  sketch  of 
each  part  in  the  same  relative  position  it  occupies  in  the  burner.  Put 
the  burner  together  again,  and  connect  with  the  gas  supply. 

Close  the  holes  in  the  bottom  of  the  burner,  turn  on  the  gas, 
and  hold  a  lighted  match  slightly  below  the  mouth  of  the  burner. 
Result?  Open  the  holes  carefully  until  the  luminous  flame  just  dis- 
appears. Result?  Open  the  holes  as  far  as  possible.  Result?  Now 
close  the  holes  to  the  position  where  a  small  luminous  cone  is  left  in 
the  flame.  Place]  a  cold  surface,  as  a  piece  of  bright  iron  or  porce- 
lain, upon  the  cone  for  a  minute.     Result? 

Introduce  quickly  into  the  center  of  the  non-luminous  or  Bun- 
sen flame  just  above  the  top  of  the  burner  the  head  of  a  match.  Re- 
sults? 

Results: — What  is  the  difference  in  the  character  of  the  flame 
when  the  holes  near  the  bottom  of  the  burner  are  closed  and  when 
they  are  open?  To  what  is  this  difference  due?  What  is  the  effect 
of  too  much  air?  Of  too  Uttle?  Is  there  any  disagreeable  effect 
attending  this  latter  feature?  What  does  the  test  with  the  match  show? 
Where  is  the  hottest  part  of  the  flame? 

EXPERIMENT  14 

Object: — To  demonstrate  the  meaning  of  kindling  temperature. 

Apparatus  and  Material: — Bunsen  burner,  wire  gauze,  match. 

Method: — ^Hold  a  piece  of  iron  wire  gauze  about  3  inches  above 
the  mouth  of  a  Bunsen  burner.  Open  the  holes  of  the  burner,  turn 
on  the  gas,  and  lower  a  lighted  match  from  above  down  to  the  center 
of  the  gauze.  Result?  After  a  few  minutes  if  the  gas  does  not  take 
fire  below  the  gauze,  light  it. 

24r- 


370  CHEMISTRY  OF  THE  FARM  AND  HOME 

Allow  the  gauze  to  cool.  Bring  it  down  upon  the  non-luminous 
flame  of  the  burner  until  the  gauze  is  three  inches  above  the  top  of  the 
burner.  Results?  Hold  the  gauze  in  place  until  it  becomes  red  hot. 
Results? 

Results: — In  the  first  instance,  why  does  the  gas  not  bum  below 
the  gauze?  In  the  second  part  of  the  experiment,  why  does  the  gas  not 
burn  above  the  gauze  until  the  latter  is  red  hot?  What  special  type 
of  lamp  makes  use  of  the  principle  that  is  involved  in  this  experi- 
ment? 

EXPERIMENT  15 

Object: — To  prepare  hydrogen. 

Apparatus  and  Material: — A  gas  generator  (see  Figure  15),  gran- 
ulated zinc,  commercial  hydrochloric  acid. 

Method: — Arrange  an  apparatus  similar  to  that  shown  in  Figure 
16.  Place  in  the  flask  about  25  grams  of  granulated  zinc.  Add  water 
through  the  thistle  tube  until  the  bottom  of  the  latter  is  immersed. 
Then  add  a  small  amount  of  commercial  hydrochloric  acid  until  the 
gas  is  evolved  rapidly.  Allow  considerable  gas  to  escape  before  col- 
lecting any.     Why? 

Fill  two  bottles  with  water  and  invert  in  the  trough  in  the  same 
manner  as  in  the  preparation  of  oxygen.  Fill  these  with  hydrogen 
and  allow  them  to  remain  in  the  trough  until  they  are  needed  for  the 
next  experiment.  Proceed  immediately  to  test  the  properties  of 
hydrogen. 

EXPERIMENT  16 

Object: — To  demonstrate  the  properties  of  hydrogen. 

Apparatus  and  Material: — Hydrogen  gas,  wood  splinters,  match. 

Method: — Grasp  the  bottom  of  one  of  the  bottles  of  the  gas 
and  keep  it  in  this  inverted  position.  Thrust  a  burning  splinter  of 
wood  up  into  the  middle  of  the  bottle  of  gas  (Figure  17).  Does  the  gas 
bum?    Does  the  sphnter  bum? 

Place  the  mouth  of  the  second  bottle  of  hydrogen  over  the  mouth 
of  an  upright  bottle  of  air.  Hold  the  bottles  together  and  reverse 
their  positions.  After  a  minute  apply  a  lighted  match  to  the  lower 
bottle.     Result?    To  the   upper.     Result? 

Results: — Does  hydrogen  bum  or  does  it  support  combustion? 
Is  it  lighter  or  heavier  than  air?  Is  its  mixture  with  air  explosive? 
Is  it  safe  to  have  lights  near  a  hydrogen  generator? 

Caution: — Keep  all  flames  at  least  three  feet  away  from  the  flask; 
in  which  hydrogen  is  being  prepared. 


EXPERIMENTS  371 

CHAPTER  III. 

EXPERIMENT  17 

Object: — To  show  some  effects  of  the  rusting  of  iron  in  the  air. 

Apparatus  and  Material: — 100  c.c.  or  200  c.c.  graduate,  clamp, 
pint  mason  jar,  muslin  cloth,  steel  wool  or  clean  iron  fihngs,  wood 
splinter. 

Method: — Force  a  wad  of  steel  wool  or  a  quantity  of  clean  iron 
filings  tied  in  a  muslin  bag  about  half  way  up  a  graduated  tube  of  100 
or  200  c.c.  capacity.  Wet  the  iron  and  clamp  the  tube  with  its  open 
end  down  in  a  vessel  of  water.  The  level  of  water  inside  the  tube 
should  be  within  the  graduations.  If  not,  remove  the  tube,  add  water 
to  it,  cover  with  the  hand  and  replace  in  the  water.  Read  the  level 
of  the  water  inside  the  tube  and  allow  the  experiment  to  stand  un- 
disturbed for  two  or  three  days.  Occasionally  feel  the  tube  near 
the  iron  mass.  Again  read  the  level  of  the  water.  Thrust  a  glow- 
ing splinter  of  wood  up  into  the  gas  remaining  in  the  tube.  Results? 
Remove  the  iron  or  steel  and  examine  carefully. 

Results: — What  are  the  results?  Is  heat  evolved  or  absorbed? 
To  what  is  the  change  in  the  iron  due?  What  does  the  change  in  the 
volume  show?    Explain  the  effect  upon  the  glowing  stick. 

EXPERIMENT  18 

Object: — To  show  whether  water  exists  in  the  atmosphere. 

Apparatus  and  Material: — Watch  glasses,  calcium  chloride. 

Method: — Several  students  may  do  this  experiment  together. 
Weigh  upon  each  of  several  watch  glasses  about  5  grams  of  calcium 
chloride.  Place  the  different  glasses  in  different  parts  of  the  room,  as 
near  a  window,  or  the  sink,  or  a  radiator,  or  in  a  cupboard.  Allow 
them  to  rehiain  in  these  positions  for  a  day.  Examine  the  glasses, 
weigh  again,  and  state  the  results.  In  case  nothing  definite  is  shown, 
allow  the  glasses  to  remain  exposed  for  another  day. 

EXPERIMENT  19 

Object: — To  show  whether  carbon  dioxide  exists  in  the  atmos- 
phere. 

Apparatus  and  Material: — 50  c.c.  beaker,  glass  tubing,  Hmewater. 

Method: — Several  students  may  do  this  experiment  together  in  a 
manner  similar  to  experiment  18.  Use  a  50  c.c.  beaker  half  full  of  per- 
fectly clear  Hmewater  instead  of  the  glass  with  calcium  chloride.  After 
a  day's  exposure  in  the  different  positions,  examine  the  beakers  and 
their  contents.     Results? 


372      CHEMISTRY  OF  THE  FARM  AND  HOME 

Place  in  a  50  c.c.  beaker  about  25  c.c.  of  perfectly  clear  limewater, 
secure  a  clean  piece  of  glass  tubing,  and  blow  into  the  liquid  for  a  few 
minutes. 

Results: — Is  there  any  similarity  between  this  result  and  that 
in  the  first  part  of  the  experiment?  What  is  the  connection  between 
the  two  parts? 

EXPERIMENT  20 

Object: — To  study  the  properties  of  acids. 

Apparatus  and  Material: — Test  tubes,  glass  rods,  dilute  hydro- 
chloric acid,  dilute  sulphuric  acid,  strong  acetic  acid,  red  and  blue 
Htmus  paper,  zinc,  limestone,  chalk,  or  marble. 

Method: — Half  fill  three  test  tubes  with  dilute  hydrochloric  acid, 
sulphuric  acid,  and  strong  acetic  acid  respectively.  Dip  a  clean  glass 
rod  into  each  acid  and  carefully  taste  it.  Dip  the  rod  a  second  time 
into  the  acid  and  transfer  a  drop  to  both  red  and  blue  htmus  paper. 
Results?  Place  a  small  piece  of  zinc  in  each  tube.  If  no  action 
results,  warm  gently.  Hold  a  lighted  match  over  the  mouth  of  the 
test  tube.  Results?  Into  fresh  portions  of  the  acids  place  a  small 
piece  of  limestone,  chalk,  or  marble.  Hold  a  glass  rod  which  has 
been  dipped  in  clear  limewater  in  the  escaping  gas.     Results? 

Results: — Describe  by  a  single  word  the  taste  of  all  the  acids 
tested.  The  effect  of  acids  upon  litmus  paper  is  quite  characteristic. 
What  conclusion  can  be  drawn  from  the  test?  What  substance  is 
evolved  from  the  action  of  the  metals  upon  acids?  Has  this  been  shown 
in  any  previous  experiment?  What  is  the  gas  liberated  from  the  cal- 
cium carbonate  by  the  acids?  What  general  statement  can  be  made, 
then,  concerning  the  properties  of  acids? 

EXPERIMENT  21 

Object: — To  study  the  properties  of  bases. 

Apparatus  and  Material: — Test  tubes,  glass  rods,  sodium  hydrox- 
ide, potassium  hydroxide,  ammonium  hydroxide,  hmewater,  red  and 
blue  litmus  paper. 

Method: — Prepare  dilute  solutions  of  sodium  and  potassium 
hydroxides  by  adding  a  very  small  piece  of  each  to  test  tubes  half 
full  of  water.  Also  half  fill  a  test  tube  of  dilute  ammonium  hydrox- 
ide and  one  with  limewater.  Apply  the  following  tests  to  these  ma- 
terials.    Rub  a  httle  of  the  hquid  between  the  fingers  and  describe 


EXPERIMENTS  373 

the  feeling.  Barely  moisten  a  glass  rod  with  each  of  the  liquids  and 
very  cautiously  taste  them.  Again  dip  the  glass  rod  in  each  liquid 
separately  and  touch  a  piece  of  red  and  blue  litmus  paper. 

Results: — Describe  the  results  of  the  testing  of  these  liquids. 
Compare  the  action  upon  litmus  paper  with  that  of  acids  upon  such 
test  paper.     What  is  the  most  striking  result  of  these  tests? 

EXPERIMENT  22 

Object: — To  study  the  properties  of  salts. 

Apparatus  and  Material: — Test  tubes,  sodium  chloride,  potassium 
sulphate,  ammonium  chloride,  barium  chloride. 

Method: — Prepare  dilute  solutions  of  sodium  chloride,  potassium 
sulphate,  ammonium  chloride,  and  barium  chloride.  In  the  same 
manner  as  in  the  tests  for  acids  and  bases  carefully  taste  each  liquid. 
Also  test  the  action  of  each  upon  both  kinds  of  litmus  paper. 

Results: — Is  there  any  general  characteristic  of  taste  as  in  the  case 
of  the  acids  and  bases?  How  does  the  action  of  these  salts  upon  lit- 
mus compare  with  the  action  of  acids  and  bases  upon  litmus? 

EXPERIMENT  23 

Object: — To  study  the  reaction  of  common  substances. 

Apparatus  and  Material:— Lemon  juice,  vinegar,  sour  milk,  borax, 
soap,  washing  soda,  sugar,  cream  of  tartar,  baking  soda,  sweet  milk, 
litmus  paper. 

Method: — Apply  the  litmus  test  to  the  substances  named  above. 

Results: — Tabulate  the  results  under  the  three  heads  of  acid, 
alkali,  and  neutral  reactions. 

EXPERIMENT  24 

Object: — To  study  the  reaction  of  acids  and  alkahes. 

Apparatus  and  Material: — Sodium  hydroxide,  hydrochloric  acid, 
litmus  paper. 

Method: — Place  50  c.c.  water  in  a  100  c.c.  evaporating  dish  and 
add  a  small  piece  of  sodium  hydroxide.  When  the  alkali  is  dissolved, 
add  hydrochloric  acid  drop  by  drop,  constantly  testing  with  htmus 
paper  until  the  solution  just  reacts  acid.  Evaporate  to  dryness  by 
heating  over  a  wire  gauze,  finally  heating  the  dish  until  the  yellow  color 
disappears.  Test  a  portion  of  the  residue  with  litmus.  Result? 
Taste  a  little  of  the  residue. 

Results: — What  is  the  effect  of  the  residue  upon  litmus?  What 
does  the  residue  taste  like?  What  is  such  a  reaction  called?  Is  this 
an    appropriate    name? 


374  CHEMISTRY  OF  THE  FARM  AND  HOME 

EXPERIMENT  25 

Object: — To  demonstrate  the  properties  of  nitric  acid. 

Apparatus  and  Material: — Test  tubes,  white  quills,  wood  or  silk, 
copper  foil  or  wire,  chalk,  nitric  acid. 

Method: — Place  a  few  fragments  of  white  quills,  or  wool,  or  silk, 
in  a  test  tube.  Add  enough  dilute  nitric  acid  to  cover  the  material 
and  warm  gently.  Pour  off  the  acid  and  wash  the  substance  with 
water.     Result? 

Place  a  short  strip  of  copper  foil  or  wire  in  a  test  tube.  Add 
nitric  acid  and  warm  gently  until  the  action  starts.  Describe  all 
that  takes  place. 

Place  a  small  amount  of  chalk  in  a  test  tube.  Add  a  small  amount 
of  dilute  nitric  acid.     Results? 

Results: — Describe  all  the  results  of  the  above  experiments.  Is 
nitric  acid  an  active  compound  or  not?  Should  one  use  care  in  working 
with  the  acid? 

EXPERIMENT  26 

Object: — To  demonstrate  the  properties  of  ammonia  gas. 

Apparatus  and  Material: — 200  c.c.  flask,  3  dry  bottles,  deep  dish 
or  tin,  wood  sphnters,  concentrated  ammonium  hydroxide,  hydro- 
chloric acid,  sodium  hydroxide  solution,  litmus  paper. 

Method: — Place  50  c.c.  of  concentrated  ammonium  hytiroxide 
in  a  200  c.c.  flask.  Heat  gently  to  drive  off  the  gas.  Fill  three 
bottles  separately  with  the  gas  by  holding  the  empty  bottles  directly 
over  the  mouth  of  the  flask.  Why  does  the  ammonia  replace 
the  air? 

Plunge  the  mouth  of  one  of  the  bottles  of  gas  under  water.  Al- 
low this  to  stand  for  some  time  and  proceed  with  the  remainder  of 
the  experiment.  Slowly  introduce  into  the  second  bottle  a  hghted 
splinter  of  wood.  Describe  the  behaviour  of  the  gas  on  the  instant 
when  it  comes  in  contact  with  the  flame.  Does  the  gas  burn?  Does 
it    support    combustion? 

Pour  a  few  drops  of  strong  hydrochloric  acid  into  an  empty  warm 
dry  bottle.  Cover  with  a  glass  plate,  invert,  and  stand  upon  the 
third  bottle  of  ammonia  gas.  Remove  the  glass  plate  and  hold  the 
bottles  together  by  grasping  them  firmly  about  their  necks.  Results? 
Is  there  any  evidence  of  chemical  action?  Is  heat  evolved?  Allow 
the  white  product  to  settle,  remove  some,  and  warm  in  a  test  tube 
with  a  httle  sodium  hydroxide  solution.  What  is  the  gas  given  off? 
What  was  the  wh?te  product? 


EXPERIMENTS  375 

Return  to  the  first  bottle  of  gas  which  is  standing  in  water.  Place 
a  glass  plate  under  the  mouth  of  the  bottle  and  invert  it  with  the 
water  remaining  in  the  bottle.  Test  it  with  a  piece  of  Htmus  paper. 
Result? 

Results: — Is  ammonia  gas  soluble  in  water?  To  what  degree? 
How  is  this  shown?  How  does  the  water  solution  affect  htmus 
paper?  What  other  experiment  gave  a  similar  result?  What  is  the 
relation  of  ammonia  to  combustion?  What  is  the  reaction  with 
hydrochloric   acid? 

EXPERIMENT  27 

Object: — To  study  the  properties  of  nitrates. 

Apparatus  and  Material: — Test  tube,  iron  pan,  sodium  nitrate, 
sulphate  of  iron,  concentrated  sulphuric  acid,  charcoal,  powdered 
potassium  nitrate. 

Method: — Place  a  small  amount  of  sodium  nitrate  solution  in  a 
test  tube.  Add  a  crystal  of  ferrous  sulphate  and  shake  the  mixture 
until  the  sulphate  is  dissolved.  Now  add  cautiously  2  or  3  c.c.  of 
strong  sulphuric  acid.  Incline  the  tube  so  that  the  acid  will  flow 
down  to  the  bottom  of  the  solution  without  mixing  with  it.  What 
is  the  result? 

Heat  a  piece  of  charcoal  in  the  burner.  Lay  it  upon  an  iron  pan 
and  very  carefully  sprinkle  powdered  potassium  nitrate  upon  the  hot 
surface.     Stand    back    when    the    action    begins. 

Results: — Observe  and  describe  the  reaction.  Is  it  violent?  Is 
it  rapid?  What  is  the  color  of  the  flame  and  the  effect  upon  the  char- 
coal. What  causes  the  action?  What  rather  common  substance  de- 
flagrates when  made  to  react  in  a  similar  manner? 

CHAPTER  IV. 

EXPERIMENT  28 

Object: — To    prepare    chlorine. 

Apparatus  and  Material: — Gas  generating  flask  (see  Figure  23), 
3  dry  bottles,    manganese   dioxide,    concentrated   hydrochloric   acid. 

Method: — Arrange  an  apparatus  hke  that  shown  in  Figure  24. 
Place  in  the  flask  5  grams  of  manganese  dioxide  (lumps)  and  add  through 
the  funnel  20  c.c.  concentrated  hydrochloric  acid.  Warm  the  flask 
gently  and  fill  three  dry  bottles  with  the  chlorine.  Keep  the  bottles 
stoppered  until  ready  to  use.  Pass  the  gas  from  the  generator  into 
15  c.c.  cold  water  in  a  test  tube  for  5  minutes.    When  through,  discon- 


376  CHEMISTRY  OF  THE  FARM  AND  HOME 

nect  the  apparatus  at  once  and  wash  the  manganese  dioxide  which 
remains  with  two  portions  of  water. 

Caution: — Avoid  inhaUng  chlorine.  If  some  of  the  gas  has  been 
accidently  inhaled,  breathe  ammonia  gas  very  cautiously  after  re- 
moving the  stopper  from  a  bottle  of  ammonia  water. 

EXPERIMENT  29 

Object: — To  show  the  properties  of  chlorine. 

Apparatus  and  Material: — Splinter  of  wood,  dyed  calico,  news- 
paper, paper  with  ink  writing. 

Method: — What  is  the  color  and  the  odor  of  the  gas?  (Do  not 
smell  the  gas  directly.  Enough  generally  escapes  into  the  room  to  give 
the  test.)  Thrust  a  lighted  sphnter  of  wood  down  into  a  bottle  of  the 
gas.  Does  the  gas  bum  or  does  it  support  combustion?  Put  into  a 
bottle  of  the  gas  a  small  piece  of  wet  dyed  cloth,  a  small  piece  of  dry 
dyed  cloth,  a  paper  with  print  and  a  paper  with  ink.  Allow  to  remain 
15  minutes.  Results?  Into  another  bottle  of  chlorine  pour  some 
powdered  antimony  which  has  previously  been  slightly  heated. 

Results: — Is  chlorine  an  active  element?  What  evidence  shows 
this?  In  the  bleaching  experiment,  what  factor  seems  to  be  essential 
in   order   to   accomplish   the   bleaching? 

EXPERIMENT  30 

Object: — To  prepare  hydrochloric  acid  and  study  its  properties. 

Apparatus  and  Material: — Gas  generating  flask  (see  Figure  24), 
2  dry  bottles,  common  salt,  dilute  sulphuric  acid,  red  and  blue  litmus 
paper. 

Method: — Arrange  an  apparatus  like  that  in  Figure  23,  but  omit- 
ting the  wash  bottle.  Place  about  15  grams  of  common  salt  in  the 
flask  and  add  enough  water  to  just  cover  the  bottom  of  the  thistle 
tube.  Now  add  about  25  c.c.  of  dilute  sulphuric  acid  (1  part  acid  and 
1  part  water)  and  heat  gently.  Collect  two  dry  bottles  of  the  gas  by 
downward  displacement  of  air.  Into  one  of  the  jars  place  small  pieces 
of  moistened  blue  and  red  litmus  paper.  Place  the  second  bottle  mouth 
down  in  a  dish  of  water.  Test  the  reaction  of  the  water  solution  with 
pieces  of  red  and  blue  litmus  paper. 

Results: — Describe  the  results  of  the  experiment.  Is  the  gas 
very  soluble  in  water?  Does  the  water  solution  have  the  same  reaction 
as  the  gas  itself? 

EXPERIMENT  31 
Object: — To  study  the  bleaching  action  of  bleaching  powder. 


EXPERIMENTS  Zll 

Apparatus  and  Material: — 2  small  beakers,  bleaching  powder, 
dilute   sulphuric   acid,    dyed   calico. 

Method: — Take  two  small  beakers;  in  one  place  some  dilute 
sulphuric  acid  and  in  the  other  some  bleaching  powder  and  water. 
Saturate  a  piece  of  dyed  cahco  in  the  acid;  then  dip  it  into  the  bleaching 
powder  paste.  If  necessary,  repeat  this  operation  several  times. 
Finally  wash  the  cloth  in  a  basin  of  water. 

Results: — What  happens  to  the  color  in  the  cloth?  Does  there 
seem  to  be  a  gas  liberated  from  the  powder  by  the  action  of  the  acid? 
What  is  it?     How  can  you  prove  it? 

EXPERIMENT  32 

Object: — To  show  the  presence  of  chlorides  in  water. 

Apparatus  and  Material: — ^Dilute  solution  common  salt,  dilute 
silver  nitrate,  drinking  water,  nitric  acid. 

Method: — Prepare  a  dilute  solution  of  common  salt.  To  10  c.c. 
of  this  add  3  drops  of  nitric  acid  and  about  5  c.c.  of  dilute  silver  nitrate 
solution.  Warm  the  mixture  shghtly  and  shake  strongly.  What  is 
the  character  of  the  precipitate?  Secure  a  sample  of  drinking  water. 
To  about  25  c.c.  add  3  drops  of  nitric  acid  and  5  c.c.  of  silver  nitrate 
and  proceed  as  above.  If  no  definite  result  is  shown,  evaporate  100  or 
200  c.c.  of  the  drinking  water  to  a  small  bulk  and  repeat  the  test. 
Results? 

EXPERIMENT  33 

Object: — To  study  the  degree  of  chemical  affinity  of  one  element 
for  another. 

Apparatus  and  Material: — 6-inch  test  tubes,  dilute  solutions  of 
potassium  iodide  and  potassium  bromide,  chlorine  water,  chloroform. 

Method: — Prepare  a  dilute  solution  of  potassium  bromide  and  place 
IQ  c.c.  in  a  6  inch  test  tube.  Add  about  2  c.c.  of  the  chlorine  water 
prepared  in  a  previous  experiment  and  shake  the  mixture  well.  Re- 
sult? Now  add  about  2  c.c.  of  chloroform  to  the  mixture  and  again 
shake  well.  Result?  Repeat  the  test,  but  use  a  dilute  solution  of  po- 
tassium iodide  instead  of  the  potassium  bromide.     Result? 

Results: — Does  this  experiment  confirm  your  conclusion  that 
chlorine  is  or  is  not  an  active  element?  What  were  the  substances 
liberated  by  the  action  of  the  chlorine  water  upon  the  potassium 
•  salts  -taken?  If  chlorine  is  able  to  displace  an  element  from  its  com- 
pound with  another  element,  which  is  the  more  active  chemical  sub- 
stance, the  chlorine  or  the  displaced  element? 


378  CHEMISTRY  OF  THE  FARM  AND  HOME 

EXPERIMENT  34 

Object: — To  study  the  effect  of  heating  sulphur. 

Apparatus  and  Material: — 6-iiich  test  tubes,  powdered  sulphur. 

Method: — Fill  a  test  tube  H  full  of  sulphur,  hold  it  at  an  indined 
angle  and  heat  carefully.  As  the  temperature  gradually  increases, 
note  all  the  changes  that  occur.  What  happens  to  the  sulphur?  What 
is  the  color  of  the  new  form?  Is  it  thick  or  thin?  Pour  a  drop  into 
water.  What  is  the  color  of  the  product?  Is  it  soft  or  hard?  Now 
heat  the  sulphur  further.  What  happens?  Heat  still  more  until  the 
sulphur  begins  to  boil;  then  pour  it  into  cold  water.  Result?  What 
is  the  color  of  the  product?  Is  it  hard  or  soft?  Elastic  or  brittle? 
Keep  this  sample  for  several  weeks,  if  necessary,  noting  any  changes 
that  occur  upon  standing.     Results? 

EXPERIMENT  35 
Object: — To  study  the  properties  of  sulphur  dioxide. 
Apparatus  and  Material: — Piece  of  crayon  with  hollowed  end,  dry 
bottles,  powdered  sulphur,  red  and  blue  litmus  paper,  pink  flower  or 
old  straw. 

Method: — Place  about  1  gram  of  sulphur  in  a  hollowed  crayon. 
Heat  in  the  flame  until  it  burns  briskly  and  then  lower  it  into  a  bottle 
of  air.  Allow  the  sulphur  to  burn  as  long  as  it  will,  covering  the  bot- 
tle with  a  cardboard.  What  are  the  products  of  this  action?  Lower 
pieces  of  moistened  red  and  blue  litmus  paper  into  the  bottle.  Result? 
Moisten  a  pink  flower  or  piece  of  old  straw,  place  in  the  bottle,  and 
allow  to  remain  there  for  an  hour  or  more.     Result? 

EXPERIMENT  36 

Object: — To  study  the  properties  of  sulphuric  acid. 

Caution: — Never  pour  water  into  the  acid. 

Apparatus  and  Material: — 2  beakers,  fine  glass  rod,  strong  sul- 
phuric acid,  red  and  blue  litmus  paper,  barium  chloride  solution, 
sugar,  boiling  water. 

Method: — Prepare  a  small  amount  of  dilute  sulphuric  acid  as  fol- 
lows :  Place  50  c.c.  of  water  in  a  100  c.c.  beaker  and  add  slowly  and  cau- 
tiously 10  c.c.  of  strong  sulphuric  acid.  Note  all  that  happens.  Place 
the  hand  upon  the  outside  of  the  beaker  in  order  to  answer  this  question. 

(1)  Dip  small  pieces  of  red  and  blue  htmus  paper  into  the  diluted 
acid.  (2)  Write  with  a  fine  glass  rod,  using  the  diluted  acid,  upon  white 
paper.  Dry  the  paper  carefully  over  a  low  flame.  (3)  Take  a  few 
c.c.  of  the  diluted  acid  and  add  some  diluted  barium  chloride  solu- 


EXPERIMENTS  379 

tion.  Warm  until  a  definite  result  is  secured.  (4)  In  a  beaker  of  about 
150  c.c.  capacity  place  25  grams  of  sugar.  Add  30  c.c.  of  boiling 
water  and  place  the  beaker  upon  a  large  plate  or  piece  of  old  paper. 
VERY  CAREFULLY  add  30  c.c.  of  strong  sulphuric  acid,  standing 
as  far  back  as  possible  from  the  apparatus. 

Results: — Describe  all  the  results  of  the  different  tests.  In  part 
(4)  what  is  the  chief  substance  produced?  What  characteristic  property 
of  sulphuric  acid  does  this  reaction  illustrate? 

EXPERIMENT  37 

Object: — To  study  the  properties  of  hydrogen  sulphide. 

Apparatus  and  Material: — Gas  generating  apparatus  (see  Figure 
21),  2  dry  bottles,  ferrous  sulphide,  dilute  hydrochloric  acid,  litmus 
paper,  wood  splinter,  lead  nitrate  solution. 

Method: — Arrange  an  apparatus  similar  to  that  illustrated  in 
Figure  21.  In  the  inner  tube  place  lumps  of  ferrous  sulphide.  In  the 
outer  tube  or  bottle  place  dilute  muriatic  acid  (1  part  acid  and  1  part 
water).  Lower  the  tube  into  the  bottle,  open  the  stop  cock,  and  col- 
lect two  bottles  of  the  gas  which  is  Uberated  by  downward  displace- 
ment of  air.  In  the  first  bottle  pour  about  15  c.c.  water  and  shake. 
Note  the  action  of  the  water  upon  the  gas.  Also  test  the  reaction  of 
the  water  solution  upon  Utmus  paper.  In  the  second  bottle  lower  a 
lighted  candle  or  sphnter  of  wood.  Does  the  gas  burn  or  does  it  sup- 
port combustion?  Bring  a  cold  surface  over  the  flame.  Result? 
Pass  the  gas  from  the  generator  directly  into  a  solution  of  lead  nitrate. 
Result? 

Results: — Is  the  gas  soluble  in  water?  What  is  its  color  and  odor? 
What  is  its  effect  upon  the  solution  of  lead  nitrate? 

EXPERIMENT  38 

Object: — To    prepare    amorphous    carbon. 

Apparatus  and  Material: — Test  tubes  and  crucibles,  bits  of  wood, 
ground  bone,  starch,   and  straw. 

Method: — Fill  an  old  test  tube  about  }4  ^uU  of  bits  of  wood.  Hold 
the  tube  horizontally  and  heat.  While  continuing  the  heating,  bring 
a  burning  match  to  the  mouth  of  the  tube.  Examine  the  residue  in 
the  tube.  Heat  a  small  amount  of  ground  bone,  starch,  or  straw  in 
separate  crucibles  or  on  crucible  covers.  After  moderate  heating, 
continue  the  ignition  for  some  time. 

Results: — State  all  the  results  of  the  experiment.  How  does  the 
residue  in  the  test  tube  compare  with  the  material  from  which  it  was 


380      CHEMmTRY  OF  THE  FARM  AND  HOME 

prepared?     What  result  is  obtained  upon  the  moderate  heating  of  the 
different  materials  in  the  crucibles?     Upon  prolonged  heating? 

EXPERIMENT  39 

Object: — To  study  the  properties  of  carbon. 

Apparatus  and  Material: — Iron  dish  with  cover,  hard  glass  tube, 
powdered  wood  or  animal  charcoal,  hydrogen  sulphide  water,  litmus 
solution,  or  brown  sugar  solution,  powdered  charcoal  and  copper  oxide. 

Method: — Part  A.  Heat  some  powdered  wood  or  animal  char- 
coal for  five  minutes  in  a  covered  iron  dish.  Cool  and  add  2  c.c.  of 
the  material  to  5  c.c.  of  hydrogen  sulphide  water.  Shake  thoroughly 
and  filter.  Compare  the  odor  of  the  filtrate  with  that  of  the  original 
solution  taken.  Result?  •  Add  2  c.C;  of  the  prepared  charcoal  to  5  c. 
c.  of  litmus  solution.  Boil  and  filter.  If  the  litmus  solution  is"  not 
available  use  5  c.c.  brown  sugar  solution. 

Part  B.  Take  a  piece  of  hard  glass  tube  10  inches  long,  heat  in 
the  center  and  draw  out  into  two  ignition  tubes.  Place  in  one  a  mix- 
ture of  1  part  powdered  charcoal  and  5  parts  of  black  copper  oxide 
sufficient  to  give  a  layer  about  1  inch  in  length.  Heat  strongly  for 
about  5  minutes.  Cool  and  pour  the  residue  upon  a  piece  of  white 
paper. 

Results: — What  property  of  carbon  do  the  tests  in  part  A  demon- 
strate? In  part  B  what  is  the  new  substance  formed  in  the  tube? 
What  name  is  applied  to  such  reactions. 

EXPERIMENT  40 

Object: — To  prepare  carbon  dioxide  and  study  some  of  its  prop- 
erties. 

Apparatus  and  Material: — Gas  generating  flask  (see  Figure  16), 
3  clean  dry  bottles,  marble  or  limestone,  hydrochloric  acid,  Ume  water, 
wood  splinter. 

Method: — Arrange  an  apparatus  similar  to  that  shown  in  Figure  16. 
Carefully  place  a  few  pieces  of  broken  marble  or  limestone  in  the  flask. 
Add  through  the  tube  enough  dilute  hydrochloric  acid  to  cover  the 
bottom  of  the  tube.  Collect  the  gas  that  is  evolved  by  downward 
displacement  of  air.  Into  one  bottle  of  carbon  dioxide  add  a  few  c.  c. 
of  clear  limewater  and  shake  the  bottle.  Results?  Into  a  second 
bottle  of  the  gas  lower  a  lighted  candle  or  sphnter  of  wood.  Does 
the  gas  bum  or  does  it  support  combustion?  Into  a  clean  bottle 
of  air  lower  a  lighted  sphnter  of  wood,  allow  to  remain  there  for  a  min- 
ute or  two,  remove  and  add  a  few  c.c.  of  clear  limewater  to  the  bottle. 
Shake  and  note  the  result.  Is  there  any  relation  between  these  two 
experiments?      Blow  into  a  few  c.c.  of  clear  limewater  in  a  test  tube. 


EXPERIMENTS  381 

Result?  Is  there  any  relation  between  this  test  and  the  others?  Con- 
tinue the  blowing  through  the  limewater  until  a  second  result  is  seen. 
What  is  the  cause  of  this? 

CHAPTER  V. 
EXPERIMENT  41 

Object: — To  study  a  characteristic  test  for  sodium  and  potassium. 

Apparatus  and  Material : — Fine  iron  wire,  powdered  common  salt, 
powdered  potassium  nitrate,  a  crystal  of  potassium  dichromate. 

Method: — Part  A.  Secure  some  clean  fine  iron  wire.  Take  a 
piece  about  6  inches  long  and  bend  one  end  into  a  loop  about  %  inch  in 
diameter.  Heat  this  end  in  the  non-luminous  flame  of  a  burner  until 
there  is  no  decided  color  tinging  the  flame.  Dip  the  loop,  while  hot-, 
into  some  powdered  salt  and  again  heat  in  the  flame.  Repeat,  holding 
near  the  flame  a  small  bright  red  object,  as  a  clear  crystal  of  potas- 
sium dichromate. 

Part  B.  Take  another  clean  piece  of  iron  wire,  bum  as  before, 
and  repeat  the  experiment,  using  potassium  nitrate  in  the  loop  instead 
of  sodium  chloride.  If  a  piece  of  blue  glass  is  available,  hold  it  in  front 
of  the  flame  while  making  the  test. 

Results: — State  all  the  results  of  the  experiment. 

NOTE: — The  student  might  at  this  time  repeat  or  review  the 
experiments,  numbers  10,  21,  and  24,  upon  the  action  of  sodium  with 
water,  the  properties  of  bases  and  neutralization. 
EXPERIMENT  42 

Object:— To  ascertain  the  properties  of  limestone. 

Apparatus  and  Material : — Test  tubes,  porcelain  crucible,  hydro- 
chloric acid,  litmus  paper. 

Method: — Examine  a  small  piece  of  limestone,  observing  its  struc- 
ture, hardness  and  color.  Powder  some  and  try  to  dissolve  a  little  in 
water.  Test  the  water  and  decide  whether  the  stone  is  soluble  or 
not  as  follows:  Filter  off  a  portion  of  the  clear  solution  and  evapor- 
ate to  dryness.  Is  there  any  residue?  Try  to  dissolve  some  limestone 
in  hydrochloric  acid.  Heat  another  portion  to  as  high  a  temperature 
as  possible  in  a  porcelain  crucible.  Cool.  Observe  its  color,  struc- 
ture, and  hardness.     Add  a  little  water.     Test  with  litmus. 

Results: — State  the  results  of  all  the  tests  applied  to  the  lime- 
stone.    Is  it  affected  by  heat?     What  is  the  product  formed? 
EXPERIMENT  43 

Object: — To  study  the  properties  of  quicklime. 

Apparatus  and  Material: — Beaker,  glass  tube,  porcelain  dish, 
quicklime,  litmus  paper. 


382  CHEMISTRY  OF  THE  FARM  AND  HOME 

Method: — Part  A.  Secure  a  piece  of  quicklime  which  has  not 
been  slaked  about  as  large  as  an  English  walnut.  Descritee  its  appear- 
ance. Add  water  to  the  hme  cautiously,  drop  by  drop,  until  there  is 
evidence  of  a  reaction.  Describe  the  appearance  of  the  product. 
Add  enough  water  to  thoroughly  slake  the  hm^  and  finally  enough  to 
make  a  thin  paste.  Stir  the  mixture  well  and  filter  off  some  of  the 
liquid.  Test  with  both  kinds  of  htmus  paper.  Evaporate  a  small 
amount  to  dryness  on  a  porcelain  dish.  Taste  the  hquid  or  residue  in 
the  dish.  Blow  through  a  clean  glass  tube  into  another  portion  of  the 
"clear    limewater. 

Results: — Does  water  react  •chemically  with  quickUme?  What 
evidence  shows  this?  Is  the  slaked  lime  soluble  in  water?  Is  the 
reaction  acid,  alkali,  or  neutral?  What  happenes  when  the  breath 
is  blown  through  the  limewater?  What  happens  if  this  is  continued 
for  some  time?  What  is  the  significance  of  this  experiment  to  agri- 
culture?    Review  Experiment  19. 

Part  B.  Place  a  small  piece  of  quicklime  in  a  tin  dish  and  allow 
it  to  be  exposed  to  the  air  over  night.  Examine  the  product.  Add  a 
small  amount  of  hydrochloric  acid  to  it  carefully.  Then  add  more 
acid  until  no  more  lime  dissolves. 

Results: — Does  this  product  resemble  that  from  the  water  slaking 
of  hme?  What  is  the  gas  liberated  by  the  addition  of  the  acid?  How 
can  this  be  proved?  If  a  lime  of  good  quaUty  practically  all  dissolves 
in  acid,  is  this  sample  of  good  quahty? 

EXPERIMENT  44 

Object: — To  study  the  cause  of  the  hardness  of  waters. 

Apparatus  and  Material: — 250  c.c.  glass  stoppered  bottle,  test 
tubes,  dilute  calcium  chloride  solution,  hmewater,  natural  water,  soap 
solution. 

Method: — Part  A.  Place  10  c.c.  of  dilute  calcium  chloride  solu- 
tion in  a  250  c.c.  glass  stoppered  bottle.  Dilute  to  100  c.c.  with 
distilled  water.  Add  2  c.c.  of  castile  soap  solution  at  a  time  and  shake 
constantly  until  a  lather  is  formed  which  persists  for  5  minutes.  De- 
scribe the  results.  Is  there  any  difference  in  the  sound  of  the  liquid 
as  it  is  shaken  before  and  after  an  excess  of  soap  is  added? 

Part  B.  Take  2  c.c.  of  perfectly  clear  hme- water  and  dilute  to 
10  c.c.  Blow  through  the  hquid  for  5  or  10  minutes  and  filter.  If 
necessary,  filter  a  second  time  to  secure  a  clear  filtrate.  What  sub- 
stance is  now  present  in  the  solution?  Divide  the  solution  into  two 
parts.  Boil  one  part  for  about  one  minute.  Result?  To  the  second 
add  a  drop  or  two  of  soap  solution  and  shake  the  hquid  as  before. 


EXPERIMENTS  383 

Result?  Add  the  same  amount  of  soap  solution  to  the  boiled  portion 
and  shake.  Result?  What  is  the  difference  in  the  behavior  of  the 
two  portions?  If  necessary  add  more  soap  solution  to  the  unboiled 
portion,  a  drop  at  a  time,  and  with  constant  agitation.     Result? 

Part  C.  Repeat  the  experiment  using  a  sample  of  water  of  direct 
interest  to  the  student.  Take  100  c.c.  portions  and  add  soap  solution 
until  the  lather  persists,  trying  both  boiled  and  unboiled  water. 

Results: — What  two  substances  apparently  react  with  soap  and 
prevent  the  latter  from  giving  its  characteristic  suds  in  water?  What 
is  the  name  applied  to  this  characteristic  action?  Is  it  possible  to  de- 
stroy one  of  these  causes  by  boiling?  Is  the  sample  of  natural  water 
tested  softened  by  boiling?    Is  soft  water  desirable  in  the  home? 

Why? 

EXPERIMENT  45 

Object: — To  show  the  effect  of  certain  metals  upon  salts  of  other 
metals. 

Apparatus  and  Material : — Test  tubes,  iron  wire,  zinc  strips,  solu- 
tions of  copper  sulphate  and  lead  acetate,  hydrochloric  acid. 

Method: — Part  A.  To  a  solution  of  copper  sulphate  add  a  few 
drops  of  hydrochloric  acid.  Clean  an  iron  wire  by  rubbing  it  with  a 
cloth  dipped  in  hydrochloric  acid.  Immerse  the  clean  iron  wire  in  the 
copper  solution  and  allow  the  whole  to  stand  for  some  time.  Remove 
the  wire  from  the  solution  and  rub  the  finger  along  it. 

Results: — Describe  all  the  results  of  the  test.  What  is  the  black 
substance?     How  can  it  be  proved?     What  becomes  of  the  iron? 

Part  B.  Fill  a  beaker  nearly  full  of  dilute  lead  acetate  solution. 
Suspend  a  strip  of  clean  metallic  zinc  in  the  solution.  Allow  the 
experiment  to  stand  undisturbed  for  some  time. 

Results: — Describe   all   the   results   of   the  experiment. 
EXPERIMENT  46 

Object: — To  compare  the  heat  conductivity  of  metals. 

Apparatus  and  Material : — Iron  wire,  copper  wire,  forceps,  burner. 

Method: — Secure  a  piece  of  iron  wire  and  of  copper  wire,  as  near 
as  possible  of  the  same  gauge.  Cut  pieces  exactly  6  inches  long. 
Hold  an  end  of  the  copper  wire  in  one  hand  and  an  end  of  the  iron  wire 
in  the  other  hand.  Place  the  other  ends  of  the  wires  in  the  flame  of  a 
burner  and  continue  there  until  a  definite  result  is  secured.  Grasp  the 
end  of  each  wire  with  a  pair  of  forceps  and  hold  in  the  hottest  part  of 
the  Bunsen  flame.  Result?  If  nothing  definite  is  shown  by  this  test, 
repeat  if  possible  with  a  blast  lamp. 

Results.— Which  metal  conducts  heat  better?  Is  there  any  change 
in  that  portion  of  the  wire  heated  directly  in  the  flame?    Which  metsil 


384  CHEMISTRY  OF  THE  FARM  AND  HOME 

is  the  more  easily  fusible?     Which  metal  oxidizes  the  more   readily? 
Is  any  practical  use  made  of  this  property  in  everyday  hfe? 
EXPERIMENT  47 

Object: — To  show  some  tests  for  copper  salts. 

Apparatus  and  Material: — Copper  sulphate  solution,  ammonium 
hydroxide,  potassium  ferrocyanide,  hydrogen  sulphide  gas. 

Method: — Dissolve  a  small  amount  of  copper  sulphate  in  water. 
To  the  clear  solution  add  ammonium  hydroxide  gradually,  but  finally 
in  excess.  To  a  solution  of  copper  sulphate  add  a  few  drops  of  potas- 
sium ferrocyanide  solution.  Pass  hydrogen  sulphide  into  a  dilute  sol- 
tion  of  copper  sulphate. 

Results: — State  the  results  of  the  three  tests. 

EXPERIMENT  48 

Object: — To  prepare  sulphate  of  iron. 

Apparatus  and  Material: — 400  c.c.  beaker  or  flask,  clean  iron 
nails,  dilute  sulphuric  acid,  ammonium  hydroxide,  nitric  acid,  tannin 
solution,  young  growing  plants  of  small  grains  or  weeds. 

Method: — Part  A.  Place  20  grams  of  clean  iron  nails  in  a  400 
c.c.  flask  or  beaker.  Add  20  c.c.  dilute  sulphuric  acid  (1  part  acid  to 
5  parts  water)  and  warm  gently  until  the  evolution  of  gas  ceases.  Pour 
off  the  clear  solution  into  a  clean  beaker,  add  2  c.c.  dilute  sulphuric 
acid  and  boil.  When  the  liquid  becomes  half  the  volume  of  the  original 
allow  to  cool.  After  the  crystals  of  ferrous  sulphate  have  separated, 
pour  off  the  liquid  from  them  and  dry  in  the  air  for  a  short  time. 

Part  B.  Test  the  properties  of  the  iron  sulphate  by  dissolving 
some  of  it  in  water  and  making  the  following  tests  upon  the  solution. 
To  one  portion  add  a  few  drops  of  ammonium  hydroxide  and  boil. 
To  a  second  portion  add  2  drops  of  nitric  acid  and  boil,  then  cool  and 
add  ammonium  hydroxide  as  before.  These  two  precipitates  illustrate 
the  ferrous  and  ferric  type  of  compounds.  To  another  portion  of  the 
ferrous  sulphate  add  a  few  drops  of  tannin  solution.  If  young  growing 
plants  of  weeds  or  the  small  grains  are  available,  sprinkle  some  of  the 
solution  of  ferrous  sulphate  upon  them. 

Results: — State  the  results  of  the  different  tests.  What  common 
substance  does  the  mixture  of  ferrous  sulphate  and  tannin  resemble? 
WTiat  is  the  effect  of  the  ferrous  sulphate  upon  the  plants?  What  is 
this  compound  used  for  on  the  farm. 

EXPERIMENT  49 
Object: — To  show  the  properties  of  zinc. 
' .  Apparatus  and  Material: — Bunsen  burner  or  blast  lamp,  forc'eps, 
zinc  foil,  sodium  hydroxide,  zinc  sulphate,  hydrogen  sulphide* 


EXPERIMENTS  385 

Method: — Grasp  a  piece  of  zinc  (preferably  the  foil)  with  a  pair  of 
forceps.  Hold  it  in  the  flame  of  a  blast  lamp,  if  one  is  available.  Re- 
sult? It  is  better  to  hold  the  zinc  over  an  asbestos  sheet  or  an  iron 
pan. 

To  a  solution  of  zinc  sulphate  add  some  sodium  hydroxide.  Result? 
Add  an  excess  of  the  sodium  hydroxide  Result?  Now  pass  hydrogen 
sulphide    into    this    solution. 

Results: — What  is  a  characteristic  property  of  the  second  pre- 
cipitate? What  use  is  made  of  zinc  compounds  in  commerce  on  ac- 
count  of   this  property? 

EXPERIMENT  50 

Object: — To  show  the  properties  of  magnesium. 

Apparatus  and  Material: — Test  tubes,  magnesium  ribbon,  hydro- 
chloric acid,  dilute  sulphuric  acid,  dilute  nitric  acid. 

Method: — Repeat  the  experiment  of  burning  a  piece  of  magnesium 
ribbon  (See  Experiment  3,C.).  Place  small  pieces  of  magnesium  rib- 
bon in  three  separate  test  tubes.  To  one  add  a  small  amount  of  dilute 
hydrochloric  acid;  to  the  second  add  dilute  sulphuric  acid;  and  to  the 
third  add  a  small  amount  of  dilute  nitric  acid. 

Results: — Is  any  gas  given  off?  If  so,  what  is  it?  How  can  the 
nature  of  the  gas  be  proved? 

CHAPTER  VI. 

EXPERIMENT  51 

Object: — To  show  the  presence  of  water  in  plants. 

Apparatus  and  Materials: — A  tall,  narrow  can,  such  as  a  tin  fruit 
can,  a  test  tube,  a  one-holed  cork  to  fit  the  tube,  a  piece  of  glass  tubing 
to  fit  the  cork,  fresh  grass  or  other  soft  plant  tissue. 

Procedure: — Bend  the  tubing  through  about  120°  near  one  end 
and  insert  the  short  end  through  the  cork.  Fix  the  cork  firmly  in  the 
test  tube  and  fasten  the  latter  upright  in  the. can.  Nearly  submerge 
the  test  tube  in  water,  first  filling  it  with  finely  cut  grass  tightly 
packed.     Now  boil  the  water. 

Results: — Does  any  hquid  drop  from  the  tube?  Test  it  by  let- 
ting a  drop  fall  on  a  crystal  of  copper  sulphate  previously  heated 
to  whiteness.     What  is  it?     Why  was  the  copper  sulphate  heated? 

EXPERIMENT  52 

Object: — To  show  the  production  of  water  and  carbon  by 
heating  carbohydrates. 

Apparatus  and  Materials: — Common  sugar.  The  apparatus  of 
Experiment  51,  with  the  exception  of  the  tin  can. 

25— 


3S6      CHEMISTRY  OF  THE  FARM  AND  HOME 

Procedure: — Place  a  little  of  the  sugar,  previously  dried  in  the 
oven,  in  the  test  tube.  Connect  the  bent  glass  tube.  Heat  the  sugar 
gradually   with   a  flame. 

Results: — Observe  the  melting  and  darkening  of  the  sugar. 
Caramel  is  formed.  At  last  decomposition  begins.  Notice  the 
smoky  products  forming  in  the  tube.  What  is  the  black  material  at 
the  bottom  of  the  tube?  Does  a  liquid  drop  from  the  extended 
arm?  Test  it  with  heated  copper  sulphate  as  in  Experiment  51. 
How  was  it  formed? 

EXPERIMENT  53 

Object: — To  compare  the  amounts  of  water  in  different  plant 
tissues. 

Apparatus  and  Materials : — A  balance  weighing  to  500  grams,  two 
shallow  one  pint  tin  dishes,  a  drying  oven  regulated  to  100°  C,  whole 
com,  green  corn  fodder  or  corn  silage. 

Procedure: — Number  the  dishes  1  and  2  with  a  soft  pencil  and 
dry  them.  Add  weights  to  balance  dish  1  and  weigh  into  it  100 
grams  of  cracked  or  ground  com.  Weigh  100  grams  of  green  fodder  or 
silage  into  dish  2.  Record  as  weights  A  the  weights  of  the  dishes  and 
materials.  Dry  in  the  oven  for  24  hours,  remove  and  weigh  as  soon 
as  cool.  If  possible  the  dried  materials  should  be  cooled  in  a  desicca- 
tor.    Record  the  weights  as  weights  B. 

Results: — Subtract  the  values  B  from  the  values  A  to  find  the 
weight  of  water  lost  and  compute  the  loss  to  per  cent  of  each  of  the 
materials. 

EXPERIMENT  54 

Object: — To  compare  the  amounts  and  kinds  of  ash-forming 
substances   in   different   plant  tissues. 

Apparatus  and  Materials: — Two  small  porcelain  dishes,  a  stirring 
rod  and  brush. 

Procedure: — In  one  dish  burn  the  dried  fodder  or  silage  of  Ex- 
periment 53  to  a  gray  ash,  adding  small  portions  at  a  time.  In  the 
other  dish  burn  an  equal  weight  of  the  dry  corn.  Press  the  material 
upon  the  hot  dish  with  the  stirring  rod,  so  as  to  burn  all  particles  of 
carbon.  The  dish  should  not  be, heated  more  than  to  a  dull  redness  at 
the  bottom,  as  otherwise  some  ash  material  may  be  volatilized. 

Results: — Which  material  contains  the  more  ash? 

Try  the  solubihty  of  the  ash  in  5  c.c.  of  strong  HCl  and  about 
25  c.c.  hot  water.  Rub  the  insoluble  residue  with  the  glass  rod. 
Does  it  feel  gritty?  This  is  silica  which  forms  a  large  part  of  the  ash  of 
grass  stems. 


EXPERIMENTS  387 

EXPERIMENT  55 

Object: — To  show  the  formation  of  sugar  in  germinating  seeds. 

Apparatus  and  Materials; — Clean  sand  or  sawdust,  a  small  box, 
barley  seed,  mortar  and  pestle,  filtering  apparatus,  Fehling's  solution 
or  silver  nitrate  solution,  and  test  tubes. 

Procedure: — Select  100  plump  barley  seeds  and  divide  into  two 
equal  lots.  Soak  one  lot  in  water  for  two  hours  and  plant  in  moist 
sand  or  sawdust.  Set  in  a  dark  place,  keep  moist  and  protect  from  mice. 
When  the  plumules  are  about  an  inch  tall  remove  the  seedlings  and 
wash  away  sand  and  sawdust.  Crush  with  50  c.c.  of  water  and  a  little 
sand  in  a  mortar  and  filter  the  extract.  Crush  the  ungerminated  seeds 
in  the  same  way.  Now  add  5  c.c.  of  each  extract  to  separate  5  c.c. 
portions  of  Fehling's  solution  and  boil. 

Results: — A  brick-red  precipitate  is  cuprous  oxide,  formed  by 
the  reducing  action  of  maltose.  If  silver  nitrate  solution  treated  with 
a  few  drops  of  NH4OH  is  used  in  place  of  Fehling's  solution,  a  gray,  or 
shiny  deposit  of  silver  will  be  formed.  Which  material  contains 
the  more  sugar?  Save  the  extract  of  germinated  barley.  To  pre- 
serve it  for  a  time  place  in  a  bottle  with  a  few  drops  of  chloroform. 

EXPERIMENT  56 

Object: — To  show  that  maltose  is  formed  from  starch  by 
the  action  of  an  enzyme  in  germinating  seeds. 

Apparatus  and  Materials: — The  extract  of  germinated  barley 
prepared  in  Experiment  55,  corn  starch,  water  bath,  and  test  tubes. 

Procedure: — Boil  about  3^  gram  starch  with  50  c.c.  of  water  for 
several  minutes  Cool  and  place  about  5  c.c.  of  this  starch  paste  in 
each  of  two  test  tubes.  To  one  tube  add  10  c.c.  of  the  extract  of  germ- 
inated barley.  To  the  other  tube  add  10  c.c.  of  the  same  extract 
which  should  be  first  boiled  and  cooled.  Mark  the  two  tubes  so  that 
they  can  be  distinguished  from  each  other.  Immerse  them  for  an  hour 
in  water  kept  at  40°C.,  stirring  occasionally. 

Results: — Now  boil  to  drive  off  the  chloroform  and  test  each 
solution  for  sugar  as  in  Experiment  55.  An  enzyme  called  diastase  is 
active  in  germinating  seeds  which  contain  starch.  Its  power  is  des- 
troyed by  heat. 

EXPERIMENT  57 

Object: — To  show  the  presence  of  fat  in  seeds. 

Apparatus  and  Materials: — A  small,  wide  mouthed  bottle  with 
stopper,  a  mortar  and  pestle,  filtering  apparatus,  gasoUne,  flax  seed, 
sunflower  seed  or  soy  bean. 

Procedure: — Put  out  all  flames  on  the  laboratory  desk.  Crush 
a  small  handful  of  flax  seed  in  a  mortar.     Place  it  in  the  bottle  and  add 


388 


CHEMISTRY  OF   THE  FARM  AND  HOME 


50  c.c.  of  gasoline.  Stopper  and  shake  occasionally  for  about  an  hour. 
Filter,  taking  great  care  to  avoid  working  near  flames  with  the  in- 
flammable gasoline. 

Results: — Pour  a    few   drops   of   the   extract   on   a   dry    filter 
paper.     What  kind  of  spot  is  left  on  it?    Set  the  rest  of  the  extract 
aside  to  evaporate.     How  does  the  residue  feel?     Heat  it  till  fumes 
appear,  and  notice  the  odor.     Is  it  a  familar  one? 
EXPERIMENT  58 
Object:— To  show  the  presence  of  proteins  in  seeds. 
Apparatus    and    Materials: — Solution    of    common  salt    of    5% 
strength,  kidney  beans,  hemp  seed  or  cotton  seed  meal  and  gasoline. 
Procedure: — Crush  a  handful   of  the  seed  and  extract  it  with 
gasohne.     Pour  off  the  extract  and  spread  out  the  residue  of  the  seed 
till  the  gasohne  has  evaporated.     Shake  up  the  residue  with  salt  solu- 
tion and  let  it  stand  for  a  day  with  occasional  stirring.     Filter  the 
extract  and  pour  it  into  2  or  3  liters  of  water. 

Results: — The  sticky  mass  which  separates  is  a  globuhn.  The 
globulins  are  by  far  the  most  abundant  plant  proteins.  A  particular 
one  known  as  phaseolin  forms  -§■  of  the  kidney  bean.  Get  some  of 
your  preparation  by  filtering  or  pouring  off  the  diluted  salt  solution. 
Add  some  strong  nitric  acid  to  it  and  follow, 
carefully,  by  an  excess  of  NH4OH  or  NaOH 
solution.  The  color  changes  are  character- 
istic of  proteins. 

EXPERIMENT  59 

Object: — To  show  that  oxygen  is  set  free 

by  plants  in  the  process  of  photo-synthesis. 

Apparatus  and  Materials: — A  glass  jar  of 

about  1  gallon  capacity,  a  wide  short-stemmed 

funnel,  a  test  tube,  a  support  and  clamp,  a 

handful  of  elodea   or   some  other   vigorous 

water  plant.    (If  no  water  plants  are  available 

some  leafy  twigs  of  any  rapidly  growing  shrub 

^^^^^     may  be  used.) 

t^^K&^p^       X.  Procedure:  —  Place    the    plant 

^*-=— ^ \  fragments  in  the  jar  and  cover  them 

with  the  inverted  funnel.  The  lat- 
ter should  not  reach  to  the  top  of 
the  jar.  See  Figure.  It  should  also  be  set  on  pieces  of  glass  tub- 
ing to  raise  it  3^  inch  or  so  from  the  bottom  of  the  jar.  This  is  to 
permit  diffusion  of  air  to  the  leaves  readily.     Add  water  to  a  depth  of 


EXPERIMENTS  389 

about  3^  inch  over  the  tip  of  the  funnel.  Fill  the  test  tube  with  water 
and  invert  it  over  the  stem  of  the  funnel. 

Results : — Place  the  apparatus  in  a  well  hghted  place  and  observe 
the  bubbles  which  form.    Do  they  form  when  the  apparatus  is  darkened? 

When  the  water  has  been  displaced  from  the  test  tube,  remove 
it,  covering  with  the  thumb.  Turn  the  tube  upright  and  thrust  a  glow- 
ing splinter  into  it.     What  gas  is  present? 

EXPERIMENT  60 

Object; — To  show  that  plants  excrete  carbon  dioxide  as  a  prod- 
uct of  respiration. 

Apparatus  and  Materials: — Two  one  quart  Mason  jars  with 
covers  and  new  rubbers,  a  vigorous  plant  of  coleus  or  some  other 
rapidly  growingform,  saturated  hmewater,  a  small  bottle,  two  flat 
dishes  of  25  or  30  c.c.  capacity. 

Procedure: — Pour  25  c.c.  of  hmewater  into  each  flat  dish.  Place 
one  of  the  dishes  in  each  Mason  jar.  Place  the  plant  cutting  in  one 
jar  with  its  cut  end  resting  in  the  small  bottle  filled  with  water.  Seal 
the  jars  tightly  and  place  them  in  a  dark,  moderately  warm  place. 

Results: — Examine  the  limewater  on  the  following  day.  In 
which  bottle  is  the  more  precipitate  present?  Add  a  little  HCl  to 
it.     What  is  it  and  how  was  it  formed? 

EXPERIMENT  61 

Object: — To  show  that  certain  inorganic  elements  are  essential 
to  growth. 

Apparatus  and  Materials: — Three  one-pint  Mason  jars  and  thin 
corks  to  fit  them,  barley  or  wheat  seedlings  obtained  as  in  Experi- 
ment 55,  but  grown  in  the  light,  500  c.c.  of  0.5%  solutions  of  KNO3 
and  NaCl,  and  cotton  batting. 

Procedure: — Number  the  jars  1,  2  and  3.  Fill  1  with  water,  2 
with  KNO3  solution  and  3  with  the  NaCl.  Cut  eight  small  wedges 
from  the  circumference  of  the  cork  with  a  thin  sharp  knife,  saving  the 
wedges.  Wrap  the  seedlings  with  a  little  cotton  at  the  base  of  the 
stem  and  fix  one  in  each  cut  of  the  corks.  Cut  off  the  tips  of  the  wedges 
and  replace  them,  fixing  them  in  place  by  an  elastic  band  or  string 
around  the  circumference  of  the  cork.  Leave  the  jars  in  a  warm  light 
place  for  two  or  three  weeks,  putting  fresh  liquid  into  each  jar  every 
two  or  three  days.     Do  not  use  a  room  where  gas  is  delivered. 

Results : — What  differences  do  you  observe?  The  reserve  food  in 
the  seeds  will  keep  the  plants  growing  in  distilled  water  some  time.  Which 
salt  supplies  the  more  essential  elements  to  the  plant?  A  mixture  of 
salts  which  wiU  produce  mature  plants  in  water  culture  can  be  provided. 


390  CHEMISTRY  OF  THE  FARM  AND  HOME 

CHAPTER  VII. 
EXPERIMENT  62 

Object: — To  show  some  of  the  properties  of  sihcon  compounds 
related  to  soil  minerals. 

Apparatus  and  Materials: — Pure,  fine  sand,  Na2C03,  strong 
solutions  of  CaCl2  and  of  alum,  HCl  and  iron  crucible  or  deep  dish. 

Procedure: — See  if  three  or  four  grains  of  sand  will  dissolve  in 
hot  cone.  HCl.  Mix  about  a  gram  of  the  sand  with  20  times  its 
weight  of  solid  sodium  carbonate  and  fuse  to  a  liquid  condition  in  an 
iron  crucible.  Continue  heating  for  10  or  15  minutes.  Cool  and 
extract  the  mass  with  100  c.c.  of  boiling  water.  Filter.  The  solution 
contains  sodium  silicate  and  when  very  strong,  is  known  as  water  glass. 
To  10  c.c.  of  the  filtrate  in  a  test  tube  add  HCl  gradually.  The 
gelatinous  precipitate   is   silicic   acid.     Filter  and  wash. 

Results: — Add  a  bit  of  the  precipitate,  of  pinhead  size,  to  4  or 
5  c.c.  of  hot,  strong  Na2C03  solution.  Is  it  soluble?  What  is  formed? 
Dry  some  of  the  precipitate  in  the  oven  and  heat  it  a  moment  in  the 
flame.     Is  it  now  readily  soluble  in   strong  Na2C03  solution?      Why? 

To    5  c.c.  of  the  waterglass  solution  add  a  little  strong  CaCl2 
solution.     To    another    portion    add    alum    solution.     The    insoluble 
calcium  and  aluminium  silicates  are  abundant  among  soil  minerals. 
EXPERIMENT  63 
Object: — To  show  that  some  soil  minerals  change  soluble  phos- 
phates of  fertihzers  to  insoluble  compounds. 

Apparatus  and  Materials: — Strong  solutions  of  ferric  chloride, 
calcium  chloride  and  di-sodium  phosphate. 

Procedure: — Add  about  5  c.c.  of  the  phosphate  solution  to  the 
same  volume  of  ferric  chloride  solution.  Notice  the  color  of  the 
precipitate.  It  is  ferric  phosphate.  Repeat,  using  calcium  chloride 
in  place  of  ferric  chloride. 

Results : — What  happens  when  mono-calcium  phosphate  of  acid- 
phosphate  fertilizer  comes  in  contact  with  either  hmonite  or  calcite 
in  the  soil? 

EXPERIMENT  64 

Object: — To  test  for  organic  matter  in  soils  rich  in  humus. 

Apparatus  and  Materials : — Two  porcelain  crucibles  or  dishes  with 
covers,  samples  of  a  sandy  soil  and  rich  garden  soil  or  peat. 

Procedure: — Place  a  small  amount  of  each  soil  in  separate  dishes, 
cover  and  heat  gradually  over  the  flame. 

Results: — What  change  of  color  do  you  observe?  Is  it  equally 
intense  in  the  two  soils?     This  charring  test  is  due  to  the  separation 


EXPERIMENTS 


391 


of  carbon  from  organic  matter.     It  does  not  occur  appreciably  when 
air  is  freely  admitted  as  by  burning  in  an  open  dish.     Why? 

EXPERIMENT  65 

Object: — To  show  acid  properties  of  humus. 

Apparatus  and  Materials: — A  tall,  small  cylinder  or  wide  mouthed 
bottle,  strongest  HCl  diluted  40  times.  Strongest  ammonium  hy- 
droxide diluted  7  times  and  rich  garden  soil  or  peat. 

Procedure: — Stir  a  small  handful  of  the  air-dry  soil  with  400 
c.c.  of  dilute  HCl  for  three  or  four  minutes,  let  settle  about  15  minutes, 
and  pour  off  or  filter  away  the  acid.  Repeat  once  with  acid  and  twice 
with  water.  Add  400  c.c.  of  the  dilute  ammonium  hydroxide  solu- 
tion, stir  occasionally  for  about  an  hour,  and  let  settle  over  night. 

Results: — Draw  off  some  of  the  solution  with  a  pipette.  What 
is  its  color?  It  contains  humus  combined  with  ammonia.  Add  strong 
HCl  gradually.  Does  a  precipitate  form?  The  insoluble  humus  is 
displaced  from  its  union  with  ammonia. 

EXPERIMENT  66 

Object: — To  show  the  presence  of  nitrogen  in  humus. 
.  Apparatus  and  Materials: —  A  test  tube  with  cork  and  deUvery 
tube  so  bent  as  to  dip  into  a  second  test  tube  partly  filled  with  water. 
Rich  garden  soil  or  peat  recently  dried  in  the  oven,  and  solid  NaOH. 


Procedure: — Mix  10  grams  of  soil  with  an  equal  bulk  of  powdered 
NaOH.  Place  in  one  test  tube  inchned  upward  and  arrange  the 
dehvery  tube  to  dip  nearly  to  the  bottom  of  the  second  test  tube. 
See  Figure.       A   loose   wad   of   cotton  —  asbestos  wool  is   better — 


392  CHEMISTRY  OF   THE  FARM  AND  HOME 

should  be  placed  just  beneath  the  stopper  of  the  tube  containing  soil. 
Now  test  the  water  in  the  second  tube  with  red  litmus  paper.  It 
should  not  be  alkahne.  Gradually  heat  the  soil.  At  first  air  will  ex- 
pand and  bubble  through  the  water  in  the  second  tube.  Water  collects 
in  the  cotton.  It  comes  from  the  oxidation  of  organic  matter  in  the 
soil.  Continue  heating  the  soil  for  several  minutes.  Remove  the 
receiving  tube  and  then  remove  the  flame. 

Results; — Test  the  water  again  with  red  htmus  paper.  Is  it 
alkaline?  The  change  is  due  to  the  formation  of  ammonia  from 
organic   compounds   of   the   humus. 

EXPERIMENT  67 

Object: — To  compare  the  power  of  different  soil  constituents  to 
absorb  water. 

Apparatus  and  Materials: — Fine  sand,  clay  and  peat  which  have 
been  air-dried  by  spreading  in  a  thin  layer  on  the  laboratory  bench 
for  two  or  three  weeks.  Three  tomato  cans  of  uniform  size  and  with 
bottoms  perforated  by  small  holes,  and  a  rough  balance. 

Procedure: — Fit  a  filter  paper  into  each  can  over  the  perforated 
bottom.  Number  the  cans  1,  2  and  3.  Fill  1  with  sand,  2  with  clay 
and  3  with  peat,  rapping  each  sharply  down  once  upon  the  bench  when 
one  third,  two  thirds  and  wholly  filled.  Level  off  the  soils  and 
weigh  the  cans  and  contents.  Support  the  cans  upright  on  the  edges 
of  brick  placed  parallel  in  the  sink.  Run  water  upon  each  until  it 
drains  away  freely  from  the  bottom.     Cover  and  leave  over  night. 

Results: — Dry  the  bottoms  with  a  cloth  and  weigh.  The  gain  of 
weight  in  grams  is  equal  to  the  c.c.  of  water  retained  by  equal  vol- 
umes of  the  soils. 

What  is  the  absorbing  power  of  the  other  soils  as  compared 
with  sand. 

EXPERIMENT  68 

Object: — To  show  the  effect  of  a  soil  mulch  upon  the  loss  of  water 
from  soil  by  evaporation. 

Apparatus  and  Materials: — Loam  soil,  two  shallow  one-quart 
tin  dishes,  and  a  large  balance. 

Procedure: — Mix  the  soil.  Fill  each  pan  with  it  to  a  depth  of 
about  three  inches.  Add  the  soil  in  layers  of  about  1  inch  depth, 
moistening  each  layer  with  water  until  just  sticky.  The  water  added 
should  be  measured  and  made  equal  in  the  two  pans.  Thoroughly 
till  the  surface  inch  of  soil  in  one  pan  with  a  thin  knife  or  spatula. 
Weigh  the  pans  and  record  weights  as  weights  A.  Let  them  stand  in 
the  laboratory  for  a  day  and  weigh  again,  recording  as  weights  B. 


EXPERIMENTS  393 

Results: — Subtract  B  from  A  and  determine  whether  the  tilled 
soil  or  mulch  has  reduced  the  loss  of  water  by  evaporation. 
EXPERIMENT  69 

Object: — To  show  that  lime  flocculates  clay. 

Apparatus  and  Materials: — Clay  soil,  pulverized  quiclc  lime, 
mortar  and  pestle,  two  100  c.c.  cylinders  or  similar  tall  jars,  and  a 
500  c.c.  beaker  or  bottle. 

Procedure: — Fasten  a  rubber  cap  over  the  pestle.  Place  a  small 
handful  of  soil  in  the  mortar  and  rub  it  gently  under  the  pestle  with 
50  to  100  c.c.  of  water.  Repeat  3  times,  pouring  off  the  hquid  each 
time  into  the  beaker.  Stir  the  contents  of  the  beaker  and  let  settle  for 
5  minutes.  Without  disturbing  the  sediment  pour  about  100  c.c.  of 
the  suspended  clay  into  each  of  the  cylinders.  Add  ^  gram  of  lime 
to  one  jar  and  shake  both  jars  thoroughly  for  two  or  three  minutes. 

Results: — Let  the  cylinders  stand  and  observe  them  occasionally 
for  a  day  or  so.     What  effect  does  the  lime  have? 
EXPERIMENT  70 

Object: — To  show  that  excess  of  water  makes  the  soil  cold. 

Apparatus  and  Materials: — Air  dried  muck  or  peat,  two  cigar  boxes 
or  quart  dishes,  two  thermometers  (one  thermometer  can  be  used) 
whose  difference  of  reading  at  room  temperature  is  known. 

Procedure: — Sift  the  soil  as  fine  as  can  readily  be  done.  Fill 
each  box  with  it  compactly.  Leave  box  1  dry  but  add  to  box  2  all 
the  water  the  soil  will  absorb.  Place  in  a  sunny  spot  and  bury  the 
bulb  of  a  thermometer  just  below  the  surface  of  the  soil  in  each  box. 

Results: — After  3^  to  1  hour  read  the  temperature  and  correct 
for  any  difference  in  the  thermometers. 

The  evaporation  of  water  and  its  own  latent  heat  keep  the  soil 
cold.     What  is  the  remedy? 

CHAPTER  VIII. 
EXPERIMENT  71 

Object: — To  study  some  characteristics  of  common  fertilizer 
ingredients. 

Apparatus  and  Material: — Test  tubes,  funnel,  and  filter  papers. 
Sodium  nitrate,  ammonium  sulphate,  calcium  cyanamide,  dried  blood, 
tankage,  floats,  steamed  bone  meal,  acid  phosphate,  sulphate  of  potash, 
and  nitrate  of  potash. 

Method: — Examine  each  of  the  materials  separately  as  follows. 
State  their  color,  form,  and  general  appearance.     Allow  a  portion  of  each 


394  CHEMISTRY  OF   THE  FARM  AND  HOME 

to  be  exposed  to  the  air  over  night,  or  longer,  if  necessary.  Test 
the  solubility  of  each  in  water  as  follows.  Place  2  grams  in  a  test  tube, 
add  15  c.c.  water  and  heat,  if  necessary,  to  dissolve  the  sohd.  Filter 
off  the  clear  liquid  and  evaporate  to  dryness. 

Results: — What  substances  are  affected  by  the  atmosphere?  What 
constituent  of  the  air  is  responsible  for  this?  Is  there  any  evidence 
of  solubility  of  these  fertilizer  materials  in  water?  Which  samples 
dissolve  most  readily?  Which  samples  are  comparatively  insoluble 
in  water?  Of  what  significance  is  the  solubility  of  fertilizers  in  actual 
farm  practice? 

EXPERIMENT  72 

Object; — To  study  the  solubility  of  commercial  fertihzers  or 
mixtures. 

Apparatus  and  Material: — Watch  glass,  funnel,  filter  papers, 
water  oven,  balance  and  weights,  some  commercial  fertilizers. 

Method: — Dry  and  weigh  a  9  cm.  or  11  cm.  filter  paper.  Fit 
in  a  funnel  and  place  in  it  2  grams  of  some  commercial  fertilizer.  Pass 
through  the  filter  between  250  and  500  c.c.  distilled  water,  a  little  at 
a  time,  at  about  ordinary  temperature.  Transfer  the  filter  paper  and 
its  contents  to  a  watch  glass,  dry  in  a  water  oven,  and  weigh.  Examine 
the  insoluble  residue  and  note  whether  it  is  composed  of  bone,  blood, 
animal  refuse,  sand,  or  other  material.  Compute  the  percentage  of 
material  that  was  dissolved  by  the  water.  Repeat  the  experiment, 
using  a  different  fertilizer.  Or,  several  students,  who  are  studying 
different  samples,  can  compare  notes. 

Results: — What  conclusion  can  be  drawn  concerning  the  immed- 
iate availability  of  the  fertilizer?  From  the  character  of  the  residue, 
if  any,  what  conclusion  can  be  drawn  in  regard  to  the  value  of  the 
fertihzer  for  the  purpose  for  which  it  is  intended? 

EXPERIMENT  73 

Object: — To    study    the    availability    of   nitrogenous   fertihzers. 

Apparatus  and  Material: — Beakers,  funnels,  and  filter  papers, 
pepsin  solution,  dried  blood,  tankage,  steamed  bone  meal. 

Method: — Prepare  a  pepsin  solution  by  dissolving  5  grams  of 
commercial  pepsin  in  a  liter  of  water  and  add  1  c.c.  strong  hydro- 
chloric acid.  Place  exactly  3^  gram  of  dried  blood,  tankage,  and 
steamed  bone  meal  in  separate  beakers.  To  each  of  these  add  200  c.c. 
pepsin  solution  and  place  the  beakers  in  a  warm  position  where  the 
temperature  is  about  that  of  the  body  (40°C.).  Stir  occasionally  and, 
at  the  end  of  5  hours  or  over  night,  filter  off  the  insoluble  matter  re- 
maining in  the  beakers,  dry  and  weigh. 


EXPERIMENTS  395 

Results: — Note  the  color  of  the  solution  and  the  character  of  the 
residue.  Compute  the  percentage  of  soluble  matter.  Which  of  these 
fertilizers  do  you  conclude  is  the  most  available,  considering  the  evi- 
dence at  hand? 

EXPERIMENT  74 

Object: — To  study  the  availability  of  phosphate  fertilizers. 

Apparatus  and  Material: — Test  tubes,  funnel,  and  filter  papers, 
bone  ash,  acid  phosphate,  floats,  nitric  acid,  ammonium  molybdate. 

Method: — Test  the  solubility  of  bone  ash,  acid  phosphate,  and 
floats  in  water  and  in  nitric  acid  as  follows.  To  about  one  gram  of 
bone  ash  in  a  test  tube  add  20  c.c.  distilled  water,  heat  for  a  few  min- 
utes, and  filter.  Warm  the  filtrate  till  hot  to  the  touch  (about  50°C.) 
and  add  5  c.c.  ammonium  molybdate.  Place  the  test  tube  in  the  rack 
allow  to  stand  while  proceeding  with  the  rest  of  the  experiment.  In 
another  test  tube  treat  one  gram  of  bone  ash  with  15  c.c.  water  and 
5  c.c.  nitric  acid.  Shake  the  mixture  for  two  minutes  and  filter. 
Warm  the  filtrate  and  add  ammonium  molybdate  as  before.  Repeat 
these  tests  with  the  other  two  materials. 

Results: — State  in  which  of  these  tests  it  was  possible  to  secure 
a  result.  What  do  these  results  mean?  Compare  the  behavior  of  these 
substances  and  indicate  which  is  the  most  available.  Which  is  the 
least  available?  Which  of  these  phosphate  fertilizers  should  be  bought, 
if  immediate  returns  are  wanted?  Which  is  the  cheapest  material  to 
buy  for  the  permanent  upbuilding  of  the  soil  phosphorus? 

EXPERIMENT  75 

Object: — To  test  for  nitrates  in  fertilizers. 

Apparatus  and  Material: — Test  tubes,  funnel,  filter  papers,  5  c.c. 
pipette  (or  glass  tube),  sodium  nitrate,  ferrous  sulphate  crystals, 
sulphuric  acid,   and  several  commercial  fertilizers. 

Method: — Dissolve  a  small  piece  of  sodium  nitrate  in  about  15 
c.c.  water.  Add  to  this  solution  a  few  small  crystals  of  ferrous  sul- 
phate and  shake  the  tube  until  the  crystals  pass  into  solution.  Draw 
up  5  c.c.  strong,  sulphuric  acid  in  a  pipette,  lower  the  latter  to  the 
bottom  of  the  solution  which  has  just  been  prepared,  and  carefully 
allow  the  acid  to  flow  into  the  solution.  Remove  the  pipette  and  allow 
the  mixture  to  stand  for  a  few  minutes. 

Part  B.  Stir  2  or  3  grams  of  the  fertihzer  to  be  tested  with  about 
20  c.c.  water  for  a  few  minutes  and  filter.  Divide  the  filtrate  into 
two  equal  portions  in  test  tubes.  To  one  of  these  add  a  few  small 
crystals  of  the  ferrous  sulphate  and  shake  until  dissolved.  To  both 
portions  of  the  solution  add  5  c.c.  strong   sulphuric   acid   as  before. 


396      CHEMISTRY  OF  THE  FARM  AND  HOME 

Results: — Does  a  brown  coloration  appear  at  the  zone  of  contact 
between  the  acid  and  the  sodium  nitrate  solution?  This  is  due  to  a 
compound  formed  by  the  reaction  between  the  ferrous  sulphate  and 
nitric  acid.  How  is  the  nitric  acid  formed?  Does  any  similar  result 
occur  in  the  case  of  the  water  solution  of  the  fertilizer?  It  is  necessary 
to  carefully  distinguish  between  this  positive  test  and  any  charring 
in  the  control  tube,  that  receiving  no  ferrous  sulphate.  Such  char- 
ring may  occur  if  the  fertilizer  contains  soluble  organic  matter. 
EXPERIMENT  76 

Object: — To    test    for    ammonia   in    fertilizers. 

Apparatus  and  Material: — Test  tubes,  strong  sodium  hydrox- 
ide, ammonium  sulphate,  red  litmus  paper,  and  commercial  fertilizers. 

Method: — Prepare  a  dilute  solution  of  ammonium  sulphate.  To 
5  c.c.  of  this  solution  add  5  c.c.  of  the  strong  sodium  hydroxide.  Heat 
gently  and  cautiously  smell  the  vapors.  Suspend  a  moist  red  litmus 
paper  in  the  vapors.  Prepare  a  water  solution  of  a  fertilizer  as  in  the 
previous  experiment.  Test  this  with  the  sodium  hydroxide  as  described 
for  the  ammonium  sulphate. 

Results: — State  the  result  of  these  tests  upon  the  litmus  paper 
and  upon  the  sense  of  smell.     What  do  you  conclude  in  regard  to  the 
presence  of  ammonia  in  combination  in  the  fertilizer? 
EXPERIMENT  77 

Object: — To  test  for  organic  forms  of  nitrogen  in  fertilizers. 

Apparatus  and  Material: — Bunsen  burner,  untanned  leather,  wood 
shavings,  tallow,  wool,  blood,  and  commercial  fertilizers. 

Method: — Burn  small  pieces  of  untanned  leather,  wood  shav- 
ings, and  tallow  separately.  Observe  the  difference  in  odor  of  the 
smoke.  Test  wool  and  blood  in  the  same  way.  Also  apply  the  test 
to  various  fertilizers,  which  may  contain  blood,  tankage,  or  other 
protein  carrier  of  nitrogen,  comparing  the  odor  with  that  produced 
by  burning  wool  or  leather  at  the  same  time. 

Results: — Is  there  any  difference  in  the  character  of  the  odor 
from  the  burning  of  these  different  materials?  When  have  you  ob- 
served an  odor  like  that  of  burning  wool?  It  is  characteristic  of 
protein  materials.  What  do  you  conclude  regarding  the  presence  of 
organic  nitrogen  in  the  fertilizers  tested? 

EXPERIMENT  78 

Object: — To  test  for  potassium  in  fertilizers. 

Apparatus  and  Material: — Test  tubes,  funnel,  and  filter  papers^ 
a  saturated  solution  of  tartaric  acid,  potassium  chloride,  ammonium 
hydroxide,    ammonium   oxalate,   and   commercial   fertilizers. 


EXPERIMENTS  397 

Method: — Prepare  a  saturated  solution  of  tartaric  acid.  Add 
5  c.c.  of  this  to  an  equal, volume  of  a  solution  of  potassium  chloride. 
Place  the  test  tube  containing  the  mixture  to  one  side  and  proceed 
with  the  experiment.  Treat  2  or  3  grams  of  fertilizer  with  10  c.c. 
water  and  filter.  To  about  5  c.c.  of  the  solution  add  an  equal  volume 
of  the  saturated  tartaric  acid  solution.  If  the  fertilizers  contain  acid 
phosphate,  it  will  be  necessary  to  remove  the  calcium  from  the  solu- 
tion before  adding  the  tartaric  acid.  Do  this  by  means  of  a  slight 
excess  of  ammonium  hydroxide  and  ammonium  oxalate  solution, 
and  filter.     Test  the  filtrate. 

Results: — Does  a  precipitate  form  when  the  solutions  of  tar- 
taric acid  and  potassium  chloride  are  mixed?     This  is  not  potassium 
tartrate  but  potassium  hydrogen  tartrate,  or  acid  tartrate.     Do  you 
obtain  a  similar  result  in  testing  the  solution  of  the  fertilizer? 
EXPERIMENT  79 

Object: — To    prepare    acid    phosphate. 

Apparatus  and  Material: — Test  tubes,  funnel,  and  filter  papers, 
bone  ash,  rock  phosphate,  strong  sulphuric  acid,  and  ammonium 
molybdate. 

Method: — Thoroughly  mix  10  grams  of  bone  ash  or  rock  phosphate 
with  6  grams  of  strongest  sulphuric  acid.  Spread  the  mass  on  a  piece 
of  waste  board  to  harden.  After  24  hours  pulverize  the  mass  in  a 
mortar  and  prepare  a  solution  of  the  material  by  treating  with  20  c.c. 
water.  Make  a  similar  solution  from  10  grams  of  the  original  ma- 
terial. To  10  c.c.  of  each  solution  add  5  c.c.  ammonium  molybdate 
and  heat  to  about  50°C.  as  in  previous  experiments.  Let  stand  a  few 
minutes. 

Results: — Compare  the  amount  of  precipitate  obtained  from  the 
acid  phosphate  which  you  prepared  with  that  from  the  original  phos- 
phate material.  What  effect  does  sulphuric  acid  have  upon  the  solu- 
bility of  bone  ash  or  rock  phosphate? 

EXPERIMENT  80 

Object: — To  compare  the  effects  produced  on  plant  growth  by 
the   different   essential   elements   of   fertilizers. 

Apparatus  and  Material: — Four  boxes  or  jars  which  will  hold  10 
pounds  of  soil,  barley  or  oat  seeds,  sodium  nitrate,  potassium  chlo- 
ride,   and  sodium   hydrogen  phosphate. 

Method: — Secure  some  unman ured  loam  soil,  mix  well,  and 
weigh  out  four  10  pound  portions.  Plant  six  plump  barley  or  oat  seeds 
in  each  lot  of  soil.  Number  the  boxes  or  jars  1,  2,  3,  and  4.  Water 
them  moderately  with  the  same  volume  of  water  and  cover  until  the 


39S  CHEMISTRY  OF  THE  FARM  AND  HOME 

seedlings  break  through  the  soil.  Now  add  the  fertilizer  elements  in 
the  water  applied  as  follows:  6.1  grams  sodium  nitrate  to  box  1;  4.47 
grams  disodium  phosphate  to  box  2,  and  1.9  grams  potassium  chlo- 
ride to  box  3.  Leave  box  4  untreated  as  a  control.  Continue  the  wat- 
ering as  required  and  in  three  or  four  weeks  repeat  the  application 
of  the  fertilizers.  The  total  amounts  of  each  of  these  fertilizer  ele- 
ments will  now  have  been  1  gram  each.  Continue  the  experiment  to 
maturity  if  practicable. 

Results: — Make  notes  on  the  difference  in  growth  of  the  plants 
in  the  different  jars  as  they  approach  maturity.  What  seems  to  be 
the  chief  effect  of  each  of  the  three  essential  elements  applied?  What 
relations  have  these  effects  to  the  soil  under  examination? 


CHAPTER  IX. 

EXPERIMENT  81 

Object: — To   show   difference   in   stabihty   of   ammonium   salts. 

Apparatus  and  Materials: — Test  tubes,  ammonium  sulphate,  and 
ammonium  carbonate. 

Procedure: — Heat  about  3^  gram  of  ammonium  sulphate  in  a 
test  tube.  Notice  the  fumes  and  their  odor.  A  sublimate  of  am- 
monium bisulphate  appears  on  the  upper  cool  walls  of  the  tube.  Test 
the  fumes  with  the  moistened  htmus  paper. 

Repeat  the  test  with  ammonium  carbonate.  What  forms  on  the 
walls  of  the  test  tube?  What  are  the  other  products  of  decompo- 
sition? This  salt  gives  the  familiar  stifling  odor  to  heating  horse 
manure. 

Results: — Which  salt  is  the  more  stable  toward  heat?  Gypsum 
is  sometimes  spread  over  the  manure  to  prevent  loss  of  ammonia. 
What  more  stable  salt  does  it  form  from  the  ammonium   carbonate? 

EXPEQIMENT  82 

Object: — To  show  formation  of  ammonia  from    urea    of   urine. 

Apparatus  and  Materials: — Human  urine,  (this  is  used  because, 
like  the  urine  of  carnivorous  animals,  it  is  much  richer  in  urea  than  that 
of  the  herbivorous  farm  animals),  litmus  paper,  test  tubes,  and  wood 
ashes. 

Procedure: — Boil  5  c.c.  of  the  fresh  urine  in  a  test  tube,  and,  as  it 
approaches  dryness,  test  the  escaping  vapors  with  moist  red  litmus  paper. 
Place  a  handful  of  fine  wood  ashes  on  a  filter  and  wash  them  with 
water  until  about  50  c.c.  of  leaching  have  collected.  Return  the 
teachings  through  the  ashes  twice.  Add  5  c.c.  of  the  leachings  to  5  c. 
c.  of  the  urine  and  boil.     Test  the  vapors  with  red  htmus  paper. 


EXPERIMENTS  399 

Results : — Urea  gives  off  part  of  its  nitrogen  as  ammonia,  when 
gently  heated.  When  heated  with  alkali,  such  as  the  K2CO3  of  wood 
ashes,  it  combines  with  water  and  decomposes  to  ammonia  and  carbon 
dioxide.  This  latter  change  is  caused  also  by  bacteria  in  the  manure. 
Is  it  desirable?  Is  it  good  practice  to  add  ashes  to  manure  in  piles? 
Is  it  safe  to  add  quick  lime? 

EXPERIMENT  83 

Object:^To  compare  the  efficiency  of  different  Utters  in  ab- 
sorbing   urine   or   the   liquid   manure. 

Apparatus  and  Materials: — Wheat  straw  or  some  similar  small 
straw,  shears,  a  pail  of  water  and  a  large  shoe  box. 

Procedure: — Weigh  two  equal  quantities  of  the  straw  of  1  foot 
lengths  which  nearly  fill  the  box  when  pressed  down.  Cut  one  lot  of 
the  straw  into  pieces  about  1  inch  in  length.  Soak  the  lot  of  long  straw 
thoroughly  in  water,  drain  and  shake  off  the  surface  water  and  weigh. 
Do  the  same  with  the  cut  straw. 

Results : — Which  lot  of  straw  has  the  greater  absorbing  power? 
Does  it  pay  to  cut  the  litter  used  for  bedding? 

Peat  has  much  greater  efficiency  than  straw  as  an  absorbent. 
As  it  decays  hardly  at  all,  however,  it  should  not  be  used  in  great 
quantity  with  manure  to  be  piled.  If  so  used  it  wiU  increase  the  loss 
from  fermentation. 

EXPERIMENT  84 

Object: — To  compare  the  amounts  of  water  in  a  fermentable 
or  *'hot"  manure  and  a  non-fermentable  or  "cold"  manure. 

Apparatus  and  Materials: — Fresh  horse  manure  and  cow  manure, 
each  quite  free  from  litter,  and  two  one-pint  tin  dishes. 

Procedure: — Weigh  the  dishes,  numbering  them  1  and  2.  Fill 
number  1  with  horse  manure  packed  down  and  number  2  with  cow  ma- 
nure. Weigh  again.  Now  dry  in  the  oven  for  a  day  or  more  and 
cool.     (Cool  preferably  in  a  large  desiccator.)      Weigh. 

Results : — Divide  the  losses  of  weight  by  drying  by  the  weights 
of  the  respective  fresh  manures.  Which  manure  is  the  drier?  Which 
ferments  the  more  readily? 

EXPERIMENT  85 

Object: — To  show  the  relation  of  water  and  air  to  the  loss  pf 
nitrogen  by  fermentation  in  hot  manure. 

Apparatus  and  Materials: — Fresh  horse  manure  free  from  litter, 
two  deep  boxes  of  about  3^  bushel  capacity,  and  two  thermometers 
whose  difference  in  reading,  if  any,  is  known. 

Procedure: — Fill  one  box  with  manure,   packing  lightly.      Fill 


400      CHEMISTRY  OF   THE  FARM  AND  HOME 

the  other  box  in  layers,  wetting  and  firmly  packing  each  layer  until 
the  box  is  full.  Bury  the  bulb  of  a  thermometer  near  the  center  of  each 
box.     Place  in  warm  room. 

Results: — At  intervals  of  a  day  read  the  temperatures  of  the 
manures.  Correct  for  differences  of  reading  of  the  thermometers. 
Which  manure  has  heated  the  most? 

Watering  and  packing  deprive  some  of  the  bacteria  of  their  neces- 
sary air.     The  water  also  absorbs  heat  and  retards  chemical  changes. 

EXPERIMENT  86 

Object: — To  show  the  power  of  soil  to  absorb  ammonia  escaping 
from  manure. 

Apparatus  and  Materials: — Two  stoppered  bottles  or  jars  of  1 
pint  capacity,  moist  clay  loam,  garden  soil  or  peat,  and  powdered 
ammonium  carbonate. 

Procedure: — Cover  the  bottom  of  each  jar  with  a  thin  layer  of 
ammonium  carbonate.  To  one  jar  add  a  covering  of  the  moist  soil 
about  1  inch  deep.  Stopper  the  jars  and  leave  on  the  laboratory 
bench. 

Results: — After  an  hour  or  more  test  the  odor  in  each  jar. 
In  which  case  has  the  more  ammonia  become  free? 

EXPERIMENT  87 

Object: — To  compare  the  fertilizing  value  of  leached  with 
unleached  manure. 

Apparatus  and  Materials: — Two  strong  boxes  of  nearly  equal  size 
which  hold  50  pounds  of  loam  or  sandy  soil  each,  fresh  cow  manure 
with  urine  well  saved  by  bedding,  cheese  cloth,  tin  pan  and  well  mixed 
sandy  soil  or  loam. 

Procedure: — Weigh  out  two  fifty-pound  lots  of  soil  or  measure 
out  two  "'half-bushel  lots  of  it.  Weigh  out  two  one-pound  lots  of  the 
manure.  Mix  one  lot  of  the  manure  into  one  lot  of  soil,  place  the  mix- 
ture, with  settling,  into  one  box  and  label  it  "Unleached  manure." 
Stir  the  other  lot  of  manure  with  enough  water  to  make  it  hquid  and 
squeeze  out  the  water  through  two  or  three  layers  of  cheesecloth. 
(The  solution  will  not  filter  readily.)  Repeat  the  washing  with  water 
twice.  Mix  the  residue  of  the  manure  with  the  second  lot  of  soil. 
Fill  the  second  box  and  label  it  "Leached  Manure."  Plant  a  few 
kernels  of  corn  in  each  box,  place  in  a  warm  sunny  spot  and  keep 
well  watered. 

Results: — Which  kind  of  manure  produces  the  better  growth? 
Why? 


EXPERIMENTS  401 

CHAPTER  X. 

EXPERIMENT  88 

Object: — To  test  for  the  chief  chemical  constituents  of  bones. 

Apparatus  and  Materials: — Green  bones.  If  a  bone  cutter  can 
be  had,  they  should  be  chopped  to  small  pieces.  A  large  iron  dish  or 
crucible,  a  mortar  and  pestle,  dilute  HNO3,  strong  acetic  acid,  solu- 
tion of  ammonium  molybdate,  and  solution  of  ammonium  oxalate. 

Procedure: — Weigh  out  100  grams  of  bone.  Burn  it  thoroughly 
and  weigh  the  ash.     What  is  the  per  cent  of  ash  in  the  bone? 

Pulverize  a  httle  of  the  bone  ash  in  the  mortar.  Add  about  }/2 
gram  to  10  c.c.  of  water  in  a  test  tube  and  add  acetic  acid  until  it  is 
mostly  dissolved.  To  the  clear  solution  add  a  few  drops  of  ammonium 
oxalate  solution.     The  precipitate  is  calcium  oxalate. 

Dissolve  another  3^  gram  portion  of  the  ash  in  10  c.c.  of  dilute 
nitric  acid.  Heat  to  boiUng  and  add  5  c.c.  of  ammonium  molybdate 
solution  with  stirring.  The  yellow  compound  is  an  ammonium  salt 
of  phosphoric  and  molybdic  acids. 

Results: — What  is  the  chief  inorganic  compound  of  bones? 

EXPERIMENT  89 

Object: — To  show  the  presence  of  sulphur  in  keratin. 

Apparatus  and  Materials: — Hair  cuttings  or  shavings  of  horn  or 
hoof,  lead  acetate  solution,  concentrated  sodium  or  potassium  hy- 
droxide solution  and  concentrated  HCl. 

Procedure: — Place  about  3^  gram  of  fine  material  from  hair, 
horn  or  hoof  in  a  test  tube.  Boil  several  minutes  with  5  c.c.  of  strong 
sodium  or  potassium  hydroxide  solution,  adding  water  to  replace  any 
appreciable  loss  by  evaporation.  Cool,  dilute  with  about  an  equal 
volume  of  water,  and  make  acid  with  HCl.  Transfer  to  a  small  necked 
flask.  Moisten  a  filter  paper  with  lead  acetate  solution  and  hold  it 
over  the  neck  of  the  flask  while  boiUng  the  acidified  solution. 

Results: — The  blackening  of  the  paper  is  due  to  the  formation 
of  lead  sulphide.  It  is  caused  by  hydrogen  sulphide  set  free  from 
potassium  sulphide  by  the  HCl.  What  was  the  source  of  the  sulphur 
in  H2S? 

EXPERIMENT  90 

Object.  To  show  the  relation  in  composition  of  muscular 
tissue  and  excretory  products  of  the  kidneys  to  food  proteins. 

Apparatus  and  Materials: — Fresh  lean  meat,  fresh  human  urine, 
dilute   copper  sulphate   solution,    strong   NaOH   solution   and   cone. 
HNO3. 
26— 


402  CHEMISTRY  OF  THE  FARM  AND  HOME 

Procedure: — Review  Experiment  58  of  Chapter  6.  Add  strong 
HNO3  and  excess  of  NaOH  solution  successively  to  a  bit  of  muscle 
tissue,  heating.     What  is  its  composition? 

Boil  a  bit  of  the  tissue  with  strong  NaOH  solution.  Cool  and 
add  two  or  three  drops  of  CUSO4  solution  down  the  side  of  the  test 
tube.  What  color  appears  in  the  upper  part  of  the  liquid?  This  is 
the  biuret  test  for  proteins. 

Evaporate  a  few  c.  c.  of  urine  in  a  dish  and  heat  very  gently  till 
white  sohd  material  appears.  Take  up  in  a  little  water,  transfer  to  a 
test  tube  and  add  successively  a  Httle  NaOH  solution  and  dilute  CUSO4 
solution.     What   color   appears? 

Results: — Gentle  heat  drives  ammonia  from  urea  and  forms 
biuret?  What  do  you  judge  to  be  the  food  source  of  urea  and  related 
nitrogen  compounds  of  the  urine? 

EXPERIMENT  91 

Object: — To  test  for  the  most  abundant  inorganic  constit- 
uent of  urine. 

Apparatus  and  Materials: — Fresh  urine,  NaOH  solution,  HNO3 
and  dilute  solution  of  silver  nitrate. 

Procedure: — Make  5  c.c.  of  the  clear  urine  alkahne  with  NaOH, 
then  acid  with  HNO3.     Add  two  or  three  drops  of  AgNOs  solution. 

Results: — The  precipitate  is  silver  chloride.  What  common  salt 
do  you  judge  to  be  abundant  in  urine? 

In  human  urine  urea  forms  about  3^  and  sodium  chloride  about 
^  of  the  total  sohds. 

EXPERIMENT  92 

Object: — To  show  the  digestive   action  of  saUva  upon  starch. 

Apparatus  and  Materials: — Corn  starch  or  any  other  common 
starch,  a  small  lump  of  clean,  soft  paraffin,  a  beaker,  a  water  bath 
(for  which  any  small  tin  dish  with  perforated  cover  will  serve),  and 
filtering  apparatus. 

Procedure: — Chew  a  lump  of  paraffin  and  collect  2  or  3  c.c.  of 
filtered  saliva.  Boil  3^  gram  starch  with  50  c.c.  of  water  for  two  or 
three  minutes  and  cool.  To  10  c.c.  of  the  starch  paste  add  10  drops 
of  saHva  and  number  the  test  tube  1.  To  another  10  c.c.  of  paste  add 
10  drops  of  saliva  heated  to  boiling  and  number  the  test  tube  2.  Mix 
the  contents  of  the  tubes  and  immerse  them  in  the  water  bath  through 
a  hole  or  holes  in  the  cover.  Keep  the  bath  at  40°C.  and  leave  the 
tubes  immersed  15  to  20  minutes.  Now  test  the  contents  of  each  test 
tube  for  sugar  by  boiling  5  c.c.  with  10  c.c.  of  Fehling  solution. 

Results: — The  enzyme  diastase  of  the  saliva  converts  starch 
to  maltose^     Why  was  no  maltose  present  in  tube  2? 


EXPERIMENTS  403 

EXPERIMENT  93 

Object: — To  show  the  digestive  action  of  pepsin  in  the  gastric 
juice  upon  proteins. 

Apparatus  and  Materials: — A  fresh  pig's  stomach,  a  hard  boiled 
egg,  HCl  and  chloroform. 

Procedure: — Wash  the  stomach  and  rip  off  the  mucous  lining 
with  the  aid  of  a  sharp  knife.  (It  requires  two  persons  to  do  this 
readily.)  Mince  the  lining  in  a  meat  chopper  and  suspend  it  in  500 
c.c.  of  water  in  a  stoppered  bottle.  Add  2>^  c.c.  of  strongest  HCl 
and  5  or  10  c.c.  of  chloroform,  mix  thoroughly,  stopper  and  let  stand 
for  a  day  or  two.  Cut  the  white  of  a  hard  boiled  egg  into  small  cubes 
with  a  sharp  knife.  Place  6  cubes  in  each  of  two  test  tubes  labeled 
1  and  2.  Filter  about  25  c.c.  of  the  stomach  or  pepsin  extract  and 
place  10  c.c.  in  tube  1.  Place  10  c.c.  of  boiled  extract  in  tube  2. 
Mix  the  contents  of  the  tubes  and  keep  them  at  about  40°C.  for  a 
day,  stoppered  with  wads  of  cotton  batting. 

Results: — Do  you  observe  any  difference  in  sharpness  of  the  cor- 
ners of  cubes  in  the  two  tubes?  Filter  the  contents  and  make  the  fil- 
trates alkaline  with  NaOH.  Warm  and  add  dilute  solution  of  copper 
sulphate.  In  which  case  is  the  biuret  test  strongest?  Why  does  no 
digestion  occur  in  tube  2? 

EXPERIMENT  94 

Object: — To  show  that  carbon  dioxide  is  excreted  from  the  lungs. 

Apparatus  and  Materials: — Saturated  hme  water  freshly  filtered 
into  a  cylinder  or  tall  bottle  and  a  small  pipette  or  a  glass  tube  drawn 
out  at  one  end. 

Procedure: — Blow  the  breath  steadily  for  several  minutes  through 
the  limewater  by  means  of  the  pipette  or  tube.  Does  the  liquid  be- 
come  turbid? 

Let  the  precipitate  settle  and  then  pour  or  draw  off  nearly  all  the 
overlying  liquid.     Add  a  little  dilute  HCl.     What  happens? 

Results: — What  is  the  precipitate  and  how  was  it  formed? 

EXPERIMENT  95 

Object: — To  prepare  gelatine  from  collagen. 

Apparatus  and  Materials: — Ground  green  bones,  and  HCl. 

Procedure: — Place  a  handful  of  the  ground  bone  in  a  small  covered 
dish  and  add  just  enough  water  to  make  the  mass  stir  easily.  Add  2 
or  3  drops  of  HCl,  cover  the  dish  and  boil  for  an  hour.  Stir  occasion- 
ally and  replace  water  lost  by  evaporation.  Filter  about  5  c.c.  of  the 
extract  and  let  it  cool. 


404  CHEMISTRY  OF  THE  FARM  AND  HOME 

Results: — Does  the  '^^tract  set?  If  not,  repeat  the  boiling.  Filter 
and  test  at  3^  hour  intervals.  The  setting  of  the  cooled  extract  is  due 
to  the  formation  of  gelatine.  Horn  and  hoof  treated  in  the  same  way 
produce  glue. 

EXPERIMENT  96 

Object: — To  show  the  action  of  tannin  upon  proteins  in  tanning. 

Apparatus  and  Materials: — Fresh  eggs  and  tannin  powder. 

Procedure: — Stir  a  little  tannin  into  50  c.c.  of  hot  water,  cool 
and  filter.  Stir  about  5  c.c.  of  egg  white  into  200  c.c.  of  cold  water. 
To  10  c.c.  of  the  protein  solution  add  5  c.c.  of  tannin  solution. 

Results: — The  tannin  forms  a  precipitate  with  the  soluble  protein. 


CHAPTER  XI. 

EXPERIMENT  97 

Object: — To  show  the  presence  of  supplies  of  calcium  and 
phosphorus  in   certain  feeding  stuffs. 

Apparatus  and  Materials: — Two  small  porcelain  dishes,  wheat 
bran,  alfalfa  or  clover  hay  cut  fine,  nitric  and  acetic  acids  and  am- 
monium hydroxide,  solutions  of  ammonium  molybdate  and  ammonium 
oxalate. 

Procedure: — Bum  about  10  grams  of  bran  and  of  hay  in  separate 
dishes.  Dissolve  the  ash  in  5  c.c.  of  strong  HNO3  and  20  c.c.  of  hot 
water.  Filter  5  or  10  c.c.  of  the  solutions  into  separate  test  tubes  so 
marked  that  they  can  be  identified.  To  the  ash  solution  of  the  bran  add 
5  c.c.  of  ammonium  molybdate  solution  and  heat  until  hot  to  the  touch. 

To  the  solution  of  hay  ash  add  a  slight  excess  of  NH4OH,  testing 
with  litmus  paper.  Add  2  or  3  c.c.  of  acetic  acid  and  5  c.c.  of  am- 
monium oxalate  and  stir. 

Results : — The  yellow  precipitate  is  a  phosphorus  compound.  The 
white  precipitate  is  calcium  oxalate.  Why  are  calcium  and  phosphorus 
important  in  feeding  stuffs? 

EXPERIMENT  98 

Object: — To  show  differences  in  the  nature  of  the  ether  ex- 
tract   of    feeding    stuffs. 

Apparatus  and  Materials: — Two  small  wide  mouthed  bottles 
with  stoppers,  ether,  alcohol,  two  sets  filtering  apparatus,  corn  meal, 
and  clover  or  timothy  hay  cut  fine. 

Procedure: — Dry  the  feeding  stuffs  in  the  oven.  Place  10  grams  of 
each  in  different  dry  bottles.  Add  25  c.c.  of  ether  to  each  bottle, 
cork  and  shake  occasionally  for  about  two  hours.  (Carefully  avoid 
flames.)     Filter  into  a  wide  dish  and  allow  the  ether  to  evaporate. 


EXPERIMENTS 


405 


Results: — How  does  the  residue  feel?  Add  10  or  15  c.c.  of  strong 
alcohol  to  each  residue  and  stir.  Does  the  alcohol  take  on  a  decided 
color  in  either  case?  This  is  due  to  chlorophyll.  Which  feeding  stuff 
seems  to  contain  the   more   true   fat? 

EXPERIMENT  99 
Object: — To  separate  essential  oils  from  feeding  stuffs. 
Apparatus   and   Materials: — A   steam   distillation   apparatus   as 

shown  in  the  figure, 
fresh  clover  hay — 
sweet  clover  if  pos- 
sible— and  fresh  rape 
or  turnips. 

Procedure : — Place 
a  little  of  the  finely 
cut  feeding  material 
in  the  distillation  test 
tube.  Add  a  few  c.c. 
of  water  and  weakly 
acidify  with  sulphuric 
acid.  Distill  with 
steam  into  the  re- 
ceiving tube. 

Results : — Observe 
the  odor  of  the  first 
few  c.c.  of  distillate.  The  essential  oil  of  hay  is  a  compound  called 
coumarin. 

Repeat  the  test  with  rape  or  turnips.  The  volatile  substances 
here   are   organic  sulphur  compounds. 

EXPERIMENT  100 

Object: — To  compare  the  amount  of  crude  fiber  in  huskless 
grains  and  in  hays  and  straws. 

Apparatus  and  Materials: — Commeal,  finely  ground  corn  stover 
or  timothy  hay  or  any  common  straw,  two  flasks  of  about  500  c.c.  ca- 
pacity fitted  with  one-holed  stoppers,  a  glass  tube  about  13^  feet  long 
to  fit  each  stopper,  filtering  outfits,  and  filters  of  linen  cloth. 

Procedure: — Dry  the  feeding  stuffs  in  the  oven.  Weigh  5  grams 
of  each  feeding  stuff  into  separate  flasks  and  shake  it  with  gasoline 
in  the  usual  way  to  remove  fat.  Filter  off  the  gasoline  and  dry  the 
residues.  Return  them  to  the  flasks  and  add  200  c.c.  of  sulphuric 
acid  of  about  2  per  cent  strength  (2  c.c.  of  strongest  H2SO4  and  200 
c.c.  of  water).       Insert  the  corks  and  upright  glass  tubes  to  act  as 


406  CHEMISTRY  OF   THE  FARM  AND  HOME 

condensers  and  boil  gently  for  3^  hour.  Filter  on  cloth  and  wash  with 
hot  water,  several  times.  Return  the  residue  to  the  flasks  and  boil 
}/2  hour  with  2  per  cent  sodium  hydroxide  solution.  Filter  and  wash  as 
before. 

Results: — Which  feeding  stuff  contains  the  more  crude  fiber? 

The  dilute  alkah  dissolves  the  protein  from  the  feeding  stuffs. 
The  dilute  acid  changes  starch  to  glucose.  The  residue  is  chiefly 
cellulose. 

EXPERIMENT  101 

Object: — To  prepare  a  typical  collection  of  feeding  stuffs 
with  reference  to  supplies  of  both  protein  and  energy. 

Procedure: — Using  a  table  of  the  composition  of  feeding  stuffs 
select  three  or  four  which  fall  in  each  of  the  following  classes: 

1.  High  protein  feeds — 30  to  45%  protein. 

2.  Medium  protein  feeds — 20  to  30%  protein. 

3.  Medium  energy  feeds — 70  to   75%  cd,rbohydrates  (nitrogen- 

free  extract). 

4.  High  energy  feeds — 75  to  85%  carbohydrates. 

CHAPTER  XII. 

EXPERIMENT  102 

Object: — To  compare  the  weight  of  whole  milk  and  water. 

Apparatus  and  Materials: — Large  scales,  ten-quart  pail,  and  fresh 
whole  milk. 

Procedure: — Weigh  10  quarts  of  milk.  Now  weigh  ten  quarts 
of  water  at  the  same  temperature.  Divide  the  weight  of  milk  by  the 
weight  of  water. 

Results:  What  is  the  value  for  the  specific  gravity  of  whole 
milk?  The  greater  weight  of  the  milk  is  due  to  the  various  compounds 
dissolved  in  it.  What  effect  does  skimming  exert  on  the  specific  gravity 
of  milk?     What  is  the  effect  of  watering? 

EXPERIMNNT  103 

Object: — To    show    that    acid    causes    the    curdhng    of   milk. 

Apparatus  and  Materials: — Sweet,  skimmed  milk,  acetic  acid 
of  about  10%  strength  or  a  like  strength  of  any  of  the  common  acids, 
and  a  large  funnel  arranged  for  filtering. 

Procedure:— Add  400  c.c.  of  water  to  100  c.c.  of  milk,  having 
both  at  about  room  temperature.  After  mixing  well  add  dilute  acid 
slowly  with  constant  stirring.  After  each  small  addition  of  acid 
watch  for  the  separation  of  white  casein  particles  from  the  liquid. 

Then  add  a  few  drops  more  of  the  acid,  stir  vigorously,  allow  to 
settle,  filter.     Save  the  filtrate  and  wash  the  precipitate. 


EXPERIMENTS  407 

Results: — Treat  the  precipitate  with  strong  HNO3  followed  by 
alkali.     To  what  kind  of  compounds  does  casein  belong? 

EXPERIMENT  104 

Object: — To  show  the  presence  of  a  sugar  in  milk. 

Apparatus  and  Materials: — Filtrate  from  Experiment  103,  Feh- 
hng's  solution  or  AgNOa  solution  made  alkahne  by  NH4OH. 

Procedure: — Make  the  filtrate  neutral  or  faintly  alkaline  by 
NH4OH.  Evaporate  to  a  volume  of  10  to  20  c.c.  Filter,  if  not  clear, 
and  boil  it  with  10  c.c.  of  Fehling's  solution. 

Results: — The  reducing  substance  in  milk  is  the  di-saccharide 
sugar  called  lactose.    What  is  its  relation  to  souring? 

EXPERIMENT  105 

Object: — To  test  for  some  of  the  ash  constituents  of  milk. 

Apparatus  and  Materials: — Two  hundred  c.c.  of  skimmed  milk, 
a  small  porcelain  dish,  solutions  of  ammonium  oxalate,  ammonium 
molybdate  and  silver  nitrate,  acetic  and  nitric  acids. 

Procedure: — Evaporate  the  milk  in  a  porcelain  dish  and  dry  the 
residue  in  the  oven.  Burn  to  a  grayish  ash.  Extract  with  a  Httle 
nitric  acid  and  about  25  c.c.  of  hot  water,  and  filter.  Divide  the  fil- 
trate into  three  portions.  To  one  portion  add  a  few  drops  of  silver 
nitrate  solution;  a  white  precipitate  or  turbidity  shows  that  chlorine  is 
present.  To  a  second  portion  add  5  c.c.  of  molybdate  solution  and 
heat  just  hot  to  the  touch;  a  yellow  precipitate  or  turbidity  denotes 
the  presence  of  phosphorus.  To  the  third  portion  add  NH4OH  till 
slightly  alkaline.  A  precipitate  will  form.  Add  acetic  acid  until  the 
precipitate,  which  is  calcium  phosphate,  dissolves.  Add  a  httle  am- 
monium oxalate  solution.  A  white  precipitate  or  turbidity  shows 
the  presence  of  calcium. 

Results: — Sodium  chloride  and  phosphates  of  potassium  and  cal- 
cium are  shown  to  be  the  most  abundant  salts  in  milk. 

EXPERIMENT  106 
Object: — To  show  the  emulsified  condition  of  fat  in  milk. 
Apparatus  and  Materials: — A  httle  fresh  whole  milk,  a  compound 
microscope,  a  mounting  shde  and  cover  glass  and  vasehne. 

Procedure: — With  vasehne  draw  a  square  smaller  than  the  cover 
glass  on  the  glass  mounting  slide.  Place  a  drop  of  the  mixed  milk 
within  it  and  press  the  cover  slip  firmly  over  it.  The  vasehne  prevents 
evaporation  from  beneath  the  cover  glass  and  keeps  the  fat  globules 
quiet  in  the  field  of  the  microscope.  Focus  the  microscope  until  you 
find  the  field  dotted  with  spheres  of  various  sizes.  These  are  the  fat 
globules  suspended  in  the  niilk.     Draw  a  small  group  of  them. 


408  CHEMISTRY  OF  THE  FARM  AND  HOME 

EXPERIMENT  107 

Object: — To  show  a  difference  between  butter-fat  and  the 
fat  of  oleomargarine  in  behavior  toward  heat. 

Apparatus    and    Materials: — Small    samples     of     oleomargarine 

butter  in  good  condition  and  test  tubes. 

Procedure: — Place  a  lump  of  "oleo"  the  size  of  a  small  walnut  in 
a  test  tube  and  heat  over  the  flame.  Observe  that  the  fat  boils  with 
much  sputtering  and  httle  foam.     Test  some  butter  in  the  same  way. 

Results: — What  difference  from  the  "oleo"  do  you  observe  with 
butter?  Notice  the  foam.  This  "foam  test"  distinguishes  butter  from 
oleomargarine. 

EXPERIMENT  108 

Object: — To  show  an  important  difference  between  the  mix- 
ture of  fats  in  butter  and  that  in  oleomargarine. 

Apparatus  and  Materials: — Two  small,  long  necked  flasks,  two 
funnels,  strong  solution  of  KOH,  sulphuric  acid,  and  two  small,  narrow 
bottles  or  beakers. 

Procedure: — Melt  a  httle  "oleo"  in  one  bottle  and  butter  in  an- 
other by  setting  them  in  the  oven  for  a  few  minutes,  with  the  door 
open.  Decant  5  to  10  c.c.  of  clear  ''oleo"  fat  into  one  flask  and  of 
butter  fat;  into  the  other.  Add  20  or  30  c.c.  of  the  KOH  solution  to 
each  flask.  Place  the  funnels  in  the  necks  of  the  flask,  to  serve  as 
condensers.  Boil  gently  for  nearly  }/2  hour.  Cool,  dilute  with  an 
equal  volume  of  water  and  make  acid  with  sulphuric  acid  of  about 
50%  strength. 

Results: — Now  heat  the  two  solutions  and  observe  the  odor 
given  off.  Have  you  smelled  it  from  butter  before?  It  is  due  to  acids 
of  some  of  the  fats  in  butter  which  are  volatile  when  free.  They  be- 
come free  in  rancid  butter.  Buytric  acid  is  important  among  them. 
Butter  contains  several  fatty  acids  not  present  in  oleomargarine. 
EXPERIMENT  109 

Object: — To  show  the  volatile  nature  of  some  flavoring  com- 
pounds of  cheese. 

Apparatus  and  Materials: — A  little  strongly  flavored  cheese  and 
a  steam  distillation  apparatus  as  used  in  Experiment  99,  Chapter  XI. 
or  separating  essential  oils  from  feeding  stuffs. 

Procedure: — Mince  a  little  cheese  and  pack  it  hghtly  around  the 
steam  dehvery  tube  in  the  distilling  flask  or  test  tube.  Distill  with 
steam  until  2  or  3  c.c.  of  distillate  has  collected  in  the  receiving  tube. 
Note  the  odor  of  the  distillate.  It  is  due  to  esters  and  other  volatile 
compounds. 


EXPERIMENTS  409 

CHAPTER  XIII. 
EXPERIMENT  110 
Object: — To  show  the  production  of  dextrin  from  starch  by  the 
toasting  of  bread. 

Apparatus  and  Materials: — Six  medium  thick  shces  of  white 
bread,  filtering  apparatus  and  evaporating  dishes. 

Procedure: — Thoroughly  toast  three  slices  of  the  bread.  Chop 
the  remaining  bread  and  the  toast  fine.  Stir  each  in  500  or  600  c.c. 
of  water  for  10  minutes  or  so.  Filter  and  evaporate  the  filtrates  sepa- 
rately. 

Results: — Which  leaves  the  more  residue?  Is  the  residue  sticky 
when  it  becomes  thick?  It  consists  chiefly  of  dextrin  formed  by  heat 
from  starch. 

EXPERIMENT  111 

Object: — To  separate  pectin  from  the  turnip. 

Apparatus  and  Materials:— Strong  alcohol,  cheese-cloth,  grater, 
fresh  turnip  and  HCl  diluted  1:15. 

Procedure: — Grate  a  turnip.  Wash  the  pulp  thoroughly  with 
water,  either  on  a  large  filter  or  by  squeezing  in  two  or  three  thick- 
nesses of  cheese-cloth.  Place  the  pulp  in  about  100  c.c.  of  the  dilute 
HCl  for  2  days.  Strain  the  extract  through  cheese-cloth  and  filter 
it.  Pour  the  filtrate  into  an  equal  volume  of  strongest  alcohol  and  let 
stand   some   time. 

Results : — What  sort  of  precipitate  forms?  It  is  pectin,  derived 
from  pectose  in  the  turnip.  Pectose  causes  the  gummy  character  of 
quince  fruit.  It  produces  jellying  when  changed  to  pectin  by  boil- 
ing, but  excessive  boiling  destroys  it. 

EXPERIMENT  112 

Object: — To  show  the  relations  of  sugars,  acids  and  starch 
in  ripening  fruits. 

Apparatus  and  Materials: — Solution  of  iodine  and  potassium 
iodide.     Very  green  apples  and  ripe  apples. 

Procedure: — Cut  some  apples  of  each  kind  in  halves  across  the 
cores.  Dry  the  cut  surfaces  with  filter  paper.  Paint  them  freely  with 
the  iodine  solution. 

Results: — Which  lot  of  apples  gives  the  stronger  blue  color  of  the 
test?  Is  any  special'  figure  formed  by  the  color  of  the  test  on  the  cut 
surfaces? 

EXPERIMENT  113 

Object: — To   test   for   the   products   of   fermentation   of  sugar. 
Apparatus  and  Materials: — Molasses,  a  250  or  300  c.c.  flask   with 


410 


CHEMISTRY  OF  THE  FARM  AND  HOME 


one  holed  stopper,  a  glass  tube  fitting  the  stopper  and  bent  to  form  a 
short  and  a  long  arm  which  are  parallel.  The  short  arm  should  not 
be  more  than  two  inches  long,  the  other  should  about  equal  in  length 
the  height  of  the  flask.     A  small  cylinder  or  large  test  tube,  kerosene, 

saturated    lime  water  and 
yeast. 

Procedure: — Add  50  c.c.  of 
molasses  to  250  c.c.  of  water 
and  mix.  Nearly  fill  the 
flask  with  the  solution. 
Crumble  ^  of  a  fresh  yeast 
cake  into  the  flask.  Fix  the 
glass  tube  with  its  shorter 
arm  just  passing  into  the  neck 
of  the  flask.  Immerse  the 
long  arm  in  freshly  filtered 
limewater  in  a  cylinder. 
See  the  figure.  Cover  the 
limewater  with  a  K  inch 
layer  of  kerosene.  Leave  the  whole  apparatus  in  a  warm  place  (110 
to  120°F.)  for  3  or  4  days. 

Results: — What  change  do  you  notice  in  the  cyhnder?  Add  a 
little  strong  HCl?     What  was  the  precipitate?     How  was  it  formed? 

Place  about  100  c.c.  of  the  fermented  fluid  in  the  flask  and  distill 
about  one  third  of  it  over  into  a  clean  receiving  vessel.  Replace  this 
distillate  alone  in  the  flask  and  redistill  about  5  c.c.  Observe  the 
odor  of  the  last  distillate.  Boil  it  in  a  test  tube  and  test  the  vapors  at 
the  mouth  of  the  tube  with  a  burning  match.  What  is  the  other 
product  of  the  fermentation  besides  alcohol? 
EXPERIMENT  114 
Object: — To  show  the  chief  chemical  change  of  the  fermenta- 
tion of  alcohol. 

Apparatus  and  Materials: — A  small  open  bottle  and  the  residue 
of  fermented  sugar  solution  left  in  Experiment  113. 

Procedure: — Place  about  100  c.c.  of  the  fermented  solution  in  a 
clean  open  bottle.  Let  it  stand  several  days  in  a  warm  place.  Observe 
its  odor.  Distill  }4  of  it  in  the  apparatus  of  Experiment  113  and  test 
the  distillate  with  blue  htm  us  paper. 

Results: — Acetic  fermentation  has  taken  place  and  alcohol  has 
been  oxidized  to  acetic  acid.  (Should  the  change  not  occur  readily,  add 
a  little  mother  of  vinegar  to  the  solution.  This  will  supply  the  lacking 
bacteria.) 


EXPERIMENTS  411 

EXPERIMENT  115 

Object: — To  prepare  (synthesize)  one  of  the  esters  which  gives 
flavor  and  aroma  to  fruits. 

Procedure: — To  5  c.c.  of  alcohol  in  a  test  tube  add  5  c.c.  of  acetic 
acid  and  1  c.c.  of  sulphuric  acid.  Heat  gently  with  the  mouth  of 
the  tube  well  away  from  the  flame. 

Results: — Notice  the  fragrant  odor  given  off.      It  is  due  to  the 
ethyl-acetate,  a  salt  or  ester  formed  from  the  alcohol  and  acetic  acid. 
Amylacetate  gives  a  pear  odor.     Ethyl  butyrate  gives  a  pineapple  odor. 
EXPERIMENT  116 

Object: — To  separate  the  proteins  of  wheat  gluten. 

Apparatus  and  Materials: — A  small  pan,  strongest  alcohol  and 
one  or  two  quarts  of  wheat  flour. 

Procedure: — Add  water,  a  httle  at  a  time,  while  kneading  the 
flour  to  a  stiff  dough.  Wash  out  all  white  patches  of  starch  by  knead- 
ing the  dough  in  gently  running  water.  The  product  is  gluten.  Squeeze 
it  as  dry  as  possible.  Mince  it  thoroughly  in  9  parts  of  alcohol  diluted 
with  one  part  of  water.  Let  stand  for  a  day  with  occasional  stirring. 
Filter  and  evaporate  the  filtrate  saving  the  residue  also. 

Results: — The  filtrate  yields  gliadin.     The  residue  from  the  alco- 
hol extraction  is  glutenin.     Test  each  by  strong   HNO3  followed  by 
NH4OH.     To  what  class  of  compounds  do.  they  belong? 
EXPERIMENT  117 

Object: — To  test  for  some  of  the  food  preservatives  most  com- 
monly used. 

Apparatus  and  Materials: — A  little  powdered  borax,  formalin 
solution  of  40%  strength,  a  small  porcelain  dish,  alcohol,  ferric  chlo- 
ride, about  300  c.c.  of  sweet  unpasteurized  milk,  which  may  be  skim- 
med milk,  and  saturated  limewater. 

Procedure: — Divide  the  milk  into  three  nearly  equal  parts,  labeled 
1,  2  and  3.  To  part  2  add  about  3^  gram  of  borax  and  stir  until  dis- 
solved. To  part  3  add  10  drops  of  formalin  and  stir.  Let  stand  in  a 
warm  room  for  a  day  or  two.  Is  there  now  any  difference  in  the 
condition    of    the    three   samples? 

Evaporate  25  c.c.  of  sample  2  with  25  c.c.  of  saturated  Ume water, 
dry  in  the  oven  and  burn  to  a  gray  ash.  Add  a  few  drops  of  strong 
sulphuric  acid  and  a  few  c.  c.  of  alcohol.  Burn  the  alcohol,  while  stir- 
ring, against  a  white  background.  Watch  for  a  green  color  on  the 
edges  of  the  flames. 

Results: — ^The  green  flame  is  due  to  ethyl  borate,  an  ester  formed 
from  boric  acid  freed  from  the  borax.     What  freed  the  boric  acid? 


412      CHEMISTRY  OF  THE  FARM  AND  HOME 

Pour  10  c.c.  of  sample  3  into  a  porcelain  dish  or  thin  teacup. 
Add  10  c.c.  of  strongest  HCl  and  a  very  small  pinch  of  ferric-chloride. 
Heat  gradually  while  stirring  with  a  rotary  movement  of  the  wrist. 
Watch  for  a  violet  color  where  the  liquid  forms  a  thin  film  on  the 
sides  of  the  dish.  The  violet  color  is  a  test  for  formaldehyde,  the 
active  agent  of  formalin. 

It  will  be  well  to  test  for  these  preservatives  in  milks  prepared  by 
the  teacher.  To  make  your  conclusions  more  reliable,  always  compare 
tests  on  your  unknown  sample  with  tests  made  at  the  same  time  on 
unpreserved  milk. 

CHAPTER  XIV. 

EXPERIMENT  118 

Object: — To  show  some  differences  in  the  chemical  properties 
of  animal  and  vegetable  fibers. 

Apparatus  and  Materials: — Strongest  nitric  acid  and  ammonia, 
and  threads  of  cotton,  linen,   wool  and  silk. 

Procedure: — Burn  some  threads  of  wool  and  then  of  silk.  Notice 
the  odor  produced.  Burn  cotton  and  linen.  Do  they  burn  at  the 
same  rate  as  wool  and  silk?  Do  they  give  the  same  odor  as  the  wool 
and  silk? . 

Immerse  some  threads  of  each  kind  in  separate  portions  of  strong- 
est  NH4OH.     Which  fibers  dissolve? 

Dip  the  threads  of  the  different  fibers  in  strongest  nitric  acid  and 
then  in  ammonia.     Which  show  a  protein  test  by  turning  yellow  to 

orange? 

EXPERIMENT  119 

Object: — To   show   some   principles   of   dyeing. 

Apparatus  and  Materials: — A"  solution  of  tannin,  made  by  stirring 
a  few  grams  of  tannin  powder  in  about  200  c.c.  of  hot  water  for  some 
time,  a  ferrous  sulphate  solution  of  5  to  10  per  cent  strength,  acetic 
acid  of  5  to  10  per  cent  strength  and  cotton  cloth. 

Procedure: — Soak  a  piece  of  cotton  cloth  in  tannic  acid  solution 
and  dry  it.  Soak  it  in  ferrous  sulphate  solution  and  dry  again.  Cut 
into  two  pieces.  Immerse  one  piece  in  a  little  boiling  water  and  the 
other  in  dilute  acetic  acid. 

Results: — The  black  dye  is  ink.  Is  it  "fast"?  Why  is  the  juice 
of  lemon  a  good  remover  of  ink  stains? 

EXPERIMENT  120 

Object: — To  show  the  chemical  properties  of  some  paint  materials. 

Apparatus  and  Materials: — Olive  oil,  linseed  oil,  turpentine, 
strong  solution  of  NH4OH,  pitch  and  dry  varnish. 


EXPERIMENTS  413 

Procedure: — Paint  a  smooth  bit  of  board  with  a  coat  of  olive  oil. 
Paint  another  with  linseed  oil.  Feel  the  surface  after  a  day  or  two. 
Linseed  oil  "sets"  because  it  takes  up  oxygen  to  satisfy  some  extra 
chemical  bonds  or  affinities  which  it  has. 

Add  bits  of  pitch  and  varnish  to  a  little  turpentine.  Do  they 
dissolve?  Does  the  varnish  dissolve  in  NH4OH  solution?  Would 
you  recommend  turpentine  or  ammonia  water  for  cleaning  varnished 
surfaces? 

EXPERIMENT  121 

Object: — To  compare  the  amounts  of  free  alkali  in  different  soaps. 

Apparatus  and  Materials: — Filtering  apparatus  with  fairly  large 
funnels,  a  washing  powder,  a  high  grade  toilet  soap,  dilute  hydrochloric 
acid — 1  part  strongest  acid  diluted  by  100  parts  of  water — phenolph- 
thalein  indicator,  and  a  burette  or  dropping  device. 

Procedure: — Weigh  10  grams  of  washing  powder  into  one  filter. 
Shave  the  soap  fine  and  weigh  10  grams  into  the  other  filter.  Wash 
each  with  small  portions  of  hot  water  until  about  200  c.c.  of  washings 
have  collected.  Add  a  few  drops  of  phenolphthalein  to  each  soap 
solution  and  determine  which  requires  the  more  of  the  weak  HCl  to 
destroy  the  color. 

Results: — Disappearance  of  the  pink  color  shows  that  the  free 
alkaU  has  been  neutralized.  Which  is  the  more  alkaline,  the  soap 
or  the  powder? 

EXPERIMENT  122 

Object: — To  show  the  relation  of  heat  to  the  preparation  of 
plaster    from    gypsum. 

Apparatus  and  Materials: — Two  small  porcelain  or  metal  dishes, 
gypsum,  and  an  oven  which  can  be  heated  to  130°C. 

Procedure: — Heat  two  small  quantities  of  gypsum,  in  numbered 
dishes,  to  not  over  130°C.  Heat  dish  2  very  hot  over  a  flame.  Cool 
the  two  dishes.     Stir  the  contents  with  a  little  water  to  form  a  paste. 

Results: — Which  portion  "sets"  to  a  hard  mass?  The  product  is 
plaster  of  Paris.  The  other  portion  is  "dead-burned"  and  no  longer 
"sets." 

EXPERIMENT  123 

Object: — To  prepare  and  test  Paris  green.     (Handle  with  care!) 
Apparatus  and  Materials: — Arsenious  oxide,  commonly  known  as 

white  arsenic,  copper  acetate,  strong  NH4OH  solution  and  filtering 

apparatus. 

Procedure: — Add  0.5  gram  of  arsenious  oxide  to  25  c.c.  of  water 

and  boil  for  5  to  10  minutes.     Filter  from  any  insoluble  material. 


414  CHEMISTRY  OF  THE  FARM  AND  HOME 

Dissolve  0.75  gram  of  copper  acetate  also  in  25  c.c.  of  hot  water.     Pour 
the  boiling  hot  solutions  together  into  a  third  vessel. 

Results: — The  green  precipitate  which  forms  is  a  compound  of 
copper  with  both  arsenious  and  acetic  acids.  It  is  the  true  Paris  green. 
Test  its  solubihty  in  NH4OH  solution.  (The  antidote  for  arsenic 
poisoning  is  fresh,  moist  ferric-hydroxide.) 

EXPERIMENT  124 

Object: — To  prepare  lime-sulphur  wash  and  test  the  action  of 
air  upon  it. 

Apparatus  and  Materials: — Flowers  of  sulphur,  pulverized,  fresh 
quick-lime  (CaO),  a  dish  of  about  one  quart  capacity,  two  flat  bottomed 
dishes  eight  or  ten  inches  in  diameter,  kerosene,  HCl  and  solution  of 
barium  chloride. 

Procedure: — Add  10  grams  of  hme  to  300  c.c.  of  water  and  stir 
for  a  short  time.  Stir  in  20  grams  of  sidphur.  Heat  gradually  with 
occasional  stirring.  Finally  boil  for  }4  hour  or  more,  keeping  the 
volume  up  by  adding  water  and  stirring  frequently.  When  the  wash 
is  cool  pour  a  shallow  layer  of  it  into  each  of  two  flat  bottomed  dishes. 
Cover  the  wash  in  one  dish  with  a  layer  of  kerosene  3^  inch  or  more  in 
depth.     After  several  days  examine  the  two  dishes. 

Results : — Is  there  any  difference  in  appearance  of  the  two  sam- 
ples? Pour  off  the  wash  from  each  dish  separately,  barely  acidify 
with  HCl  and  warm.  Filter  from  residues  and  add  a  Httle  BaCl2  solu- 
tion. The  latter  reagent  gives  a  test  for  sulphates.  What  has 
happened  to  the  lime-sulphur  exposed  to  the  air? 

EXPERIMENT  125 

Object: — To  prepare  an  oil  emulsion  or  miscible  oil. 

Apparatus  and  Materials: — Fish  oil.  (Sperm  oil  will  do.)  Po- 
tassium hydroxide  solution  of  40%  strength,  kerosene  and  paraffine 
oU. 

Procedure: — Add  10  c.c.  of  oil  to  15  c.c  of  KOH  solution  and 
heat  to  300°F.  with  stirring.  Extinguish  the  flame  and  stir  in  about 
5  c.c.  of  kerosene  oil.  The  product  is  the  soap  solution.  When  this 
is  cool  mix  it  thoroughly  with  ten  times  its  volume  of  paraffine  oil. 
Dilute  it  to  4.5  liters  with  water,  stirring  vigorously. 

Results: — The  product  is  the  diluted  miscible  oil  ready  for  use. 
How  does  it  differ  from  the  oil  merely  diluted  with  water  to  an 
equal  volume?     Why  is  the  term  "miscible"  used? 

EXPERIMENT  126 
Object: — To  prepare  Bordeaux  mixture. 
Apparatus    and    Materials:  —  Pulverized    quickhme,    pulverized 


EXPERIMENTS  415 

copper-sulphate,  several  beakers  of  200  to  500  c.c.  capacity  and  two 
small  cylinders  or  tall  jars. 

Procedure: — Prepare  a  solution  of  0.65  gram  copper  sulphate  in 
400  c.c.  of  water  and  divide  into  two  equal  parts.  Prepare  two  solu- 
tions of  quicklime  each  containing  0.25  gram  of  lime  in  200  c.c.  of 
water.  Heat  one  of  the  solutions  of  lime  nearly  to  boiling  and  pour  it 
into  one  of  the  solutions  of  copper  sulphate  pour  the  other  two  solu- 
tions together  into  a  large  beaker  at  the  same  time.  Now  stir  the  two 
preparations  of  Bordeaux  mixture  and  pour  them  into  separate  tall 
jars  or  cyhnders. 

Results: — In  which  preparation  does  the  precipitate  settle  more 
slowly?  This  is  the  correctly  prepared  mixture.  The  copper  should 
be  in  insoluble  combination  with  lime  and  sulphuric  acid,  as  soluble 
copper  will  poison  the  host  plants  as  well  as  the  parasitic  fungi. 

Test  a  dilute  solution  of  copper  sulphate  with  blue  litmus  paper. 
Now  test  your  Bordeaux  mixture  in  the  same  way.  Is  it  acid  in  re- 
action? If  so,  how  would  you  precipitate  the  remaining  copper  sul- 
phate and  make  it  weakly  alkaline? 


APPENDIX 


Books  and  Bulletins  Which   Supplement    This  Textbook. 

Chapters  I— V— 
Descriptive  Chemistry.     Newell.     D.  C.  Heath  &  Co.,  Boston. 
Experimental  Chemistry.     Newell.     D.  C.  Heath  &  Co. 
College  Chemistry.     Remsen.     Henry  Holt  &  Co.,  New  York. 
General  Chemistry.     Smith.     The  Century  Co.,  New  York. 
Organic  Chemistry.     Noyes.  W.  A.      Henry  Holt  &  Co. 

Chapter  VI— 
The  Living  Plant.     Ganong.     Henry  Holt  &  Co.,  New  York. 
Plant  Physiology.  Duggar.  The  Macmillan  Co.,  New  York. 
How   Plants   Grow.    Johnson.     Orange   Judd  Co.,    New   York. 

Chapter  Vn— 
The  Soil.     King.     The  Macmillan  Co. 
Soils  and  Soil  Fertility.     Whitson  &  Walster.     The  Webb  Pub.  Co., 

St.  Paul. 
First  Principles  of  Soil  Fertilitv.  Vivian.     Orange  Judd  Co. 
Soils.     Lyon,  Fippin  &  Buckman.     The  Macmillan  Co. 

Chapter  VHI— 
Manures  and  Fertihzers.     Wheeler.     The  Macmillan  Co. 
Soils  and  Fertilizers.     Snyder.     The  Macmillan  Co. 
Fertilizers  and  Crops.     Van  Slyke.     Orange  Judd  Co. 

Chapter  IX— 
Manures  and  Fertilizers.     Wheeler.     The  Macmillan  Co. 
Farm  Manure.     Thorne.     Orange  Judd  Co. 
Barnyard  Manure.     Beal.    Farmers'  Bulletin  192,  U.  S.  Dept.  Agr., 

Washington,  D.  C. 

Chapter  X— 
The  Feeding  of  Animals.     Jordan.     The  Macmillan  Co. 
Feeds  and  Feeding.     Henry  &  Morrison.  The  Authors.     Madison,  Wis. 

Chapter  XI— 
Elementary  Treatise  on  Stock  Feeds  and  Feeding.     Halligan.     The 

Chemical  Publishing  Co.,   Easton,   Pa. 

27—  417 


418  CHEMISTRY  OF   THE  FARM  AND  HOME 

The  Principles  of  Horse  Feeding.     Langworthy.     Farmer's  Bulletin  170. 
The  Computations  of  Rations  for  Farm  Animals  by  the  Use  of  Energy 
Values.     Armsby.     Farmers'  Bulletin  346. 

Chapter  XII— 
Dairy  Chemistry.     Snyder.     The  Macmillan  Co. 
Milk  and  Its  Products,     Wing.     The  Macmillan  Co. 
Household  Tests  for  Oleomargarine  and  Renovated  Butter.     Patrick. 

Farmers'  Bulletin  131. 

Chapter  XIII— 

The  Principles  of  Human  Nutrition.     Jordan.     The  Macmillan  Co. 

Food  Products.     Sherman.     The  Macmillan  Co. 

Human  Food.     Snyder.     The  Macmillan  Co. 

The  Function  and  Uses  of  Food.  Langworthy,  Circular  46  (revised), 
Office  of  Experiment  Stations,  Washington,  D.  C. 

Food  Customs  and  Diet  in  American  Homes.  Langworthy,  Circular 
110,  Office  of  Experiment  Stations. 

Beans,  Peas,  and  Other  Legumes  as  Food.     Abel.  Farmers' Bulletin  121. 

Principles  of  Nutrition  and  Nutritive  Value  of  Foods.  Atwater.  Farm- 
ers' Bulletin  142. 

Cereal  Breakfast  Foods.  Woods  and  Snyder,  Farmers'  Bulletin  249. 

Nuts  and  Their  Uses  as  Food.     Jaffa,  Farmers'  Bulletin  332. 

Bread  and  Bread  Making.     Atwater,  Farmers'  Bulletin  389. 

Cheese  and  Its  Economical  Use  in  the  Diet.  Langworthy  and  Hunt. 
Farmers'  Bulletin  487. 

Canning  Tomatoes  at  Home  and  in  Club  Work.  Breazeale  and  Benson. 
Farmers  Bulletin  521. 

Chapter  XIV— 

Textile  Fibers.     Matthews.     Wiley  and  Sons,  New  York. 

Dyes  and  Dyeing.     Pellew.     McBride,  Nast  &  Co.,  New  York. 

The  Chemistry  of  Cooking  and  Cleaning.  Richards  and  Elliott.  Home 
Science  Pub.  Co.,  Boston,  Mass. 

The  Chemistry  and  Testing  of  Cement.  Desch.  Edwin  Arnold,  Lon- 
don, England. 

The  Spraying  of  Plants.     Lodeman.     The  Macmillan  Co. 

Important  Insecticides.     Marlatt.     Farmers'  Bulletin  127. 

Fungicides.     Waite.     Farmers'  Bulletin  243. 

Some  Common  Disinfectants.     Dorset.     Farmers'  Bulletin  345. 

Practical  Methods  of  Disinfecting  Stables.  Pope.  Farmers'  Bulletin 
480. 


APPENDIX 


419 


Composition 

of  Soils  of  Different  Types. 

Soluble  in  hot  23%  HCl 

Total 

1 

Type  of  Soil 

1 

1 

a 

3 

'I 

c 

I 

s 

3 

s 

a 
2, 

m 

3 
u 

1 

02 

1 

2 

3 

Approximate 
Weight  per 
Cubic  Foot 

% 

% 

% 

% 

% 

% 

% 

% 

% 

Pounds 

A  sandy  soil 

5.35 
52.36 
81.53 
27.70 

6.39 
27.28 
20.05 

0.13 
0.45 
0.27 
0.37 
0.04 
0.56 
0.24 

0.34  0.14 
1.74  1.12 
0.36  0.06 
0.49  0.23 
0.02!0.02 
0.820.78 
1.550.33 

0.85 
2.92 
1.82 
2.04 
0.28 
6.50 
1.87 

0.06 
0.17 
0.14 
0.15 
0.01 
0.05 
0.10 

0.04 
0.04 
0.01 
0.02 
trace 
0.03 
0.01 

0.04 
0.38 
0.62 
'0.38 
0.05 
i0.20 
0.29 

0.47 
5.34 
15.00 
5.12 
0.70 
1.09 
2.35 

100 

A  clayey  soil 

73 

45 

A  virgin  prairie  soil 

A  cotton  raising  soil 

A  fruit  raising  soil 

An  average  fertile  soil 

65 
90 
83 
85 

Average  Composition  of  Fresh  Manures. 


Animal 

Water 

% 

Nitrogen 

% 

Phosphorus 

% 

Potassium 

% 

Cow 

77.0 
67.5 
70.0 
73.0 
64.0 

0.44 
1.27 
0.58 
0.45 
0.83 

0.07 
0.36 
0.12 
0.08 
0.10 

0.33 

Hen ,.. 

Horse 

0.23 
0  44 

Pig 

0.50 

Sheep 

0  56 

Mixed  farm  manure 

75.9 

0.45 

0.09 

0.43 

Digestibility  of  Feeding  Stuffs. 


Feeding  Stuff 


Animal 


Coefficient  of  Digestion 


Ash 


Protein 


Crude 
Fiber 

% 


Nitrogen 
FreeExtract 

% 


Fat 


Cornmeal  . . . 

Clover  hay.  . 
Potatoes .  .  . . 

Timothy  hay 
Wheat  bran . 


Ruminant 

Horse 

Pig 

Ruminant 
Horse 

Ruminant 

Horse 

Pig 

Ruminant 
Horse 

Ruminant 
Pig 


29. 


44. 


32.8 
34.0 


67.9 
75.6 
86.1 

58.0 
56.0 

44.7 
88.0 
84.5 

46.9 
21.2 

77.8 
75.1 


29.4 


54.2 
37.0 


52.5 
42.6 


28.6 
33.0 


94.6 
95.7 
94.2 

64.4 
63.0 

90.4 
99.0 
98.1 

62.3 
47.3 

69.4 
65.5 


92.1 
73.1 
81.7 

55.2 
29.0 

13.0 


52.2 
47.3 


68.0 
71.8 


420 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Feeding  Standards  for  Some  Animals. 
Daily  Ration  for  lOCO  lbs.  Weight 


Total  Dry 
Matter 

Lbs. 

Digestible  Organic  Matter 

Nutritive 
Ratio 

Kind  of  Animal 

Protein 
Lbs. 

Carbohy- 
drates 
Lbs. 

Fat 
Lbs. 

20 
26 

25 

29 
23 
30 

28 

1.5 
2.5 

1.6 

2.5 
1.5 
3.0 
3.5 

9.5 
13.3 

10.0 

13.0 
12.0 
15.0 
14.5 

0.4 
0.8 

0.3 

0.5 
0.3 
0.5 
0.6 

1:7 

Heavy  work     . . . 

1:6 

Milch  cow-Daily  milk  yield 
11  lbs 

1:6.7 

Milch  cow-Daily  milk  yield. 
22  lbs 

1:5.7 

Sheep-Fine  wool^fl 

Fattening  early 

Fattening  late 

1:8.5 
1:5.4 
1:4.5 

Growing  Beef  Cattle 
Age  (mos.)      Weight    (lbs.) 
2  to    3                    165 
6  to  12                    550 
18  to  24                    935 

23 
25 
24 

4.2 
2.5 
1.8 

13.0 
13.2 
12.0 

2.0 
0.7 
0.4 

1:4.2 
1:6.0 
1:7.2 

Composition  and  Fertility  Content  of  Feeding  Stuffs. 


Feeding  Stuff 


Alfalfa  hay 

Barley  grain 

Barley  straw 

Brewer's  grains.  . 

Corn  grains 

Corn  silage 

Corn  stover 

Clover  hay  (red) . 
Cotton  seed  meal 

Gluten  feed 

Linseed  meal .  .  .  . 

Oat  grain 

Oat  straw 

Potato 

Rutabaga 

Sugar  beet 

Timothy  hay .  .  .  . 

Wheat  grain 

Wheat  bran 

Wheat  straw 


8.4 
10.9 

'8.2 
10.9 
79.1 
40.5 
15.3 

6.8 

7.8 
10.0 
11.0 

9.2 
78.9 
88.6 
86.5 
13.2 
10.5 
11.9 

9.6 


7.4 
2.4 

"3.6 
1.5 
1.4 
3.4 
6.2 
6.2 
1.1 
5.2 
3.0 
5.1 
1.0 
1.2 
0.9 
4.4 
1.8 
5.8 
4.2 


14.3 
12.4 

19.9 

10.5 

1.7 

3.8 

12.3 

45.6 

24.0 

36.1 

11.8 

4.0 

2.1 

1.2 

1.8 

5.9 

11.8 

15.4 

3.4 


^ 


25.0 
2.7 

ii.6 

2.1 
6.0 

19.7 

34.8 
5.4 
5.3 
8.4 
9.5 

37.0 
0.6 
1.3 
0.9 

29.0 
1.8 
9.0 

38.1 


O   «5 


42.7 
69.8 

51.7 
69.6 
11.0 
31.5 
38.1 
25.2 
51.2 
36.7 
59.7 
42.4 
17.3 
7.5 
9.8 
45.0 
72.0 
53.9 
43.4 


^ 


2.2 
1.8 

■5.6 
5.4 
0.8 
1.1 
3.3 
10.8 
10.6 
3.6 
5.0 
2.3 
0.1 
0.2 
0.1 
2.5 
2.1 
4.0 
1.3 


Fertility  Content 


2.15 

1.55 

1.31 

3.00 

1.82 

0.28 

0.68 

1.98 

6.87 

5.65 

5.65 

2.24 

0.62 

0.22 

0    ' 

0 

1 

2. 

2. 

0. 


.20 

f.22 
.18 
.48 
1.67 
61 


09 

3 
t    O 


0.22 
0.35 
0.13 
0.56 
0.31 
0.05 
0.08 
0.16 
1.21 
0.78 
0.78 
0.39 
0.09 
0.03 
0.05 
0.04 
0.22 
0.41 
1.26 
0.05 


1.35 
0.42 
1.73 
1.30 
0.33 
0.30 
0.76 
1.74 
1.53 
1.13 
1.13 
0.56 
1.03 
0.25 
0.40 
0.40 
1.48 
0.53 
1.34 
0.44 


APPENDIX 


421 


Production  Values  of  a  Few  Feeding  Stuffs  per  100  Pounds. 


Total   Dry 
Matter 

Lbs. 

Total 
Crude 
Fiber 

Lbs. 

Digestible 

Production 

Feeding  Stuff 

Protein 
Lbs. 

Carbohy- 
drates 
Lbs. 

Fat 
Lbs. 

Value 
Therms 

89.1 
25.6 
84.7 
91.9 
90.1 
89.0 
9.1 
86.8 
88.1 
90.4 

2.1 
5.8 

24.8 
6.4 
8.8 
9.5 
0.8 

29.6 
9.0 

38.1 

6.79 

1.21 

5.41 

19.95 

29.26 

8.36 

0.14 

2.05 

10.21 

0.37 

66.12 
14.56 
38.15 
54.22 
38.72 
48.34 
5.65 
43.72 
41.23 
38.30 

4.97 
0.88 
1.81 
5.35 
2.90 
4.18 
0.11 
1.43 
2.87 
0.40 

88.84 

Corn  silage 

14.26 

Clover  hay   . 

34  74 

Gluten  feed 

79.32 

Linseed  meal 

74.67 
66.27 

Mangel 

4.62 

Timothy  hay 

Wheat  bran 

33.56 

48.23 

Wheat^traw 

16.56 

Factors  for  Converting  Metric  into  Ordinary  Units 
1  inch  =  2.54  cm.     1  cm.  =  0.3937  inches.     For  practical  purposes  it 
is  sufficient  to  remember  that  about  2}/^  cm.  =  1  inch. 

A -liter  is  the  volume  of  a  cube  whose  side  is  10  cm.     Therefore, 
1  hter  =  1,000  cubic  centimeters; 
1  pint  =  0.5679  hter; 
1  gallon  =  4.54346  liters; 
1  hter  =  0.2201  gallon. 
The  gram  is  the  weight  of  1  c.  c.  of  pure  water  at  4^*0 . 
1  hter  of  pure  water  at  4"'  =  1  kilo  (1,000  grams). 
1  oz.  =  28.35  gms.  1  gram  =  15.432  grains. 

1  lb.  =  453.6  gms.  1  kilo  =  2.2046  lbs. 

Formulae  for  converting  Fahrenheit  Degrees  into  Centigrade, 
and  the  Reverse 

C.°  =  5/9  (F.''  -  32). 
F.°  =  9/5C.°  +  32. 

SIGNIFICANCE  OF  TERMINATIONS 

In  a  compound  composed  of  two  kinds  of  elements,  the  names 
of  both  constituents  are  generally  involved  in  the  name  of  the  com- 
pound. The  name  of  the  more  electro-negative  element  (generally  a 
non-metal)  is  usually  placed  last  and  has  its  termination  changed  to 
ide;  oxygen  forming  oxides,  chlorine,  chlorides,  etc.  The  name  of  the 
more  electro-positive  element  (generally  a  metal)  is  usually  placed  first 
and  is  either  used  unchanged  or  its  termination  changed  to  ous  or  ic, 
according  to  its  valence.  Ous  is  employed  for  lower  and  tc  for  higher 
valencies.  The  compound  SO 2  is  called  sulphurous  oxide  and  SO 3  is 
called  sulphuric  oxide. 

Prefixes  are  sometimes  used  as  di  in  carbon  dioxide,  tri  in  phos- 
phorous trioxide,  etc.  Hypo  is  used  for  lower  valencies  and  per  for 
higher,  as  CI2O,  hypochlorous  oxide,  and  Na202,  sodium  peroxide. 

In  naming  salts  containing  three  elements,  usually  only  the  names 
of  two  of  the  constituents  are  involved.  The  endings  ite  and  ate  are 
used  in  connection  with  the  name  of  the  non-metal,  ite  when  the  salt 


422 


CHEMISTRY  OF  THE  FARM  AND  HOME 


is  formed  from  an  ous  acid  and  ate  when  formed  from  an  ic  acid.  Fer- 
rous sulphite  from  sulphurous  acid  and  ferric  sulphate  from  sulphuric 
acid. 


Table  of  Atomic  Weights 


Name  Symbol  Value 

Aluminium.  . .  .Al 27.1 

Antimony Sb 120.0 

Argon A 39.88 

Arsenic As 74.96 

Barium Ba 137.37 

Bismuth Bi 208.0 

Boron B 11.0 

Bromine Br 79.920 

Cadmium Cd 112.40 

Caesium Cs 132.81 

Calcium Ca 40.07 

Carbon C 12.00 

Cerium Ce 140.25 

Chlorine CI 35.46 

Chromium .  .  .  .  Cr 52. 

Cobalt Co 58.97 

Columbium....Cb 93.5 

Copper. Cu 63.67 

Dysprosium .  .  .  Dy 162.5 

Erbium Er 165. 

Europium Eu 152.0 

Fluorine F 19.0 

Gadolinium....  Gd 157.3 

Gallium. Ga 69.9 

Germanium . . .  .  Ge 72.5 

Glucinum Gl 9.1 

Gold Au 197.2 

Helium He 3.99 

Holmium Ho 163.5 

Hydrogen H 1.008 

Indium In 114.8 

Iodine 1 126.92 

Iridium Ir 193.1 

Iron Fe 55.84 

Krypton Kr 82.92 

Lanthanum ....  La 139.0 

Lead Pb 207.10 

Lithium Li 6.94 

Lutecium Lu 174.0 

Magnesium Mg 24.32 

Manganese ....  Mn 54.93 

Mercury Hg 200.6 


Name  Symbol  Vahie 

Molybdenum .  .  Mo 96.0 

Neodymium .  . .  Nd 144.3 

Neon Ne 20.2 

Nickel Ni 58.68 

Niton    (radium 

emanation) . .  Nt 222.4 

Osmium Os 190.9 

Oxygen O.......  16.00 

Palladium Pd 106.07 

Phosphorus. . . . P 31.04 

Platinum Pt 195.2 

Potassium K 39.10 

Praseodymium  Pr 140.6 

Radium Ra 226.4 

Rhodium Rh 102.9 

Rubidium Rb 85.45 

Ruthenium. .  .  .Ru 101.7 

Samarium Sa 150.4 

Scandium Sc 44.1 

Selenium Se 79.2 

Silicon Si 28.3 

Silver Ag 107.88 

Sodium Na 23.00 

Strontium Sr 87.63 

Sulphur S 32.07 

Tantalum Ta 181.5 

Tellurium Te 127.5 

Terbium Tb 159.2 

Thallium Ti 204.0 

Thorium Th 232.8 

Thulium Tm 168.5 

Tin Sn 119.0 

Titanium Ti 48.1 

Tungsten W 184.0 

Uranium U 238.5 

Vanadium V 51.0 

Xenon Xe 30.2 

Ytterbium Yb 172.0 

Yttrium Yt 89.0 

Zinc Zn 65.37 

Zirconium Zr 90.6 


APPENDIX 


423 


Chemicals  Required  for 
(Quantities  stated  in  grams) 

Acid,  acetic  (glacial) 400 

arsenious 25 

hydrochloric     (sp.     gr. 

1.20) 2000 

nitric  (sp.  gr.  1.42).  .  .  .2000 
sulphuric  (sp.  gr.  1.84)  .2000 

tartaric,  powder 100 

Acid    phosphate    (mono-cal- 
cium phosphate) 100 

Ammonium  hydroxide  (sp.  gr. 

0.90). 2000 

Ammonium  carbonate 10 

Ammonium  chloride 100 

Ammonium  oxalate 25 

Ammonium  sulphate 100 

Alcohol  (ethyl)  95% 2000 

Alum  powder 50 

Animal  charcoal 100 

Antimony  powder 25 

Barium  chloride 50 

Bleaching  powder 200 

Blood,  dried 100 

Bone  ash 100 

Bone  meal,  steamed 200 

Borax  powder 50 

Calcium  carbonate,  chalk 200 

limestone  200 
marble...  200 

Calcium  chloride 200 

Calcium  cyanamide 200 

Calcium  hydroxide  (lime-water; 

Charcoal 100 

Chloroform 50 

Clay 50 

Copper  wire 200 

Copper  oxide 50 

Copper  sulphate 100 

Cream  of  tartar 100 

Ether 100 

Floats     (powd.     rock    phos- 
phate)   200 

Formalin  (formaldehyde) 50 

Fehling's    solution,    parts   A 

andB,  each 200 

Ferric  chloride 25 

Ferrous  sulphate 100 

Fish  oil 100 

Gasoline 

Gypsum 50 

Iodine 25 


a  Class  of  10  Students 

Iron  filings 100 

Iron  powder 200 

Iron  wire,  stout 100 

Iron  sulphide 500 

Kerosene 

Lime  (quicklime) 500 

Lead  foil 30 

Lead  acetate 50 

Linseed  oil 25 

Litmus  paper,  blue  and  red, 
each  5  vials. 

Magnesium  ribbon 10 

Magnesia  (calcined) 50 

Manganese  dioxide 200 

Molasses 

Molybdic  acid 30 

Olive  oil 25 

Paraffin  oil 3000 

Pepsin 25 

Phenolphthalein 5 

Picture  wire 

Pitch.. 

Potassium  bromide 30 

chlorate 500 

chloride.. 100 

ferrocyanide 100 

iodide.. 30 

hydroxide 500 

nitrate 200 

sulphate 500 

Sand  (pure) 500 

Silver  nitrate 10 

Soap,  castile 100 

Sodium,  metal 10 

bicarbonate 100 

carbonate 100 

chloride 500 

hydroxide 500 

nitrate 200 

phosphate   (di-sod-    . 

ium) 25 

Solder 50 

Sugar  (sucrose) 1000 

Sulphur  (flowers) 200 

Tankage 200 

Tannin 10 

Tin.. 30 

Varnish 

Vaseline 

Zinc,  granulated 500 

Zinc,  sheet 100 


424 


CHEMISTRY  OF  THE  FARM  AND  HOME 


PREPARATION  OF  SPECIAL  REAGENTS 
Fehling's  Solution 
Part  A.     6.928  grams  pure  copper  sulphate  crystals  dissolved  in 
water  and  made  to  100  c.c. 

Part  B.     35.  6  grams  of  powdered  sodium-potassium  tartrate  and 
10  grams  sodium  hydroxide  dissolved  in  water  and  made  to  100  c.c. 
For  use,  equal  volumes  of  parts  A  and  B  are  mixed. 

Iodine  Solution 
5  grams  iodine  and  10  grams  potassium  iodide  dissolved  in  85  c.c. 
of  water. 

Ammonium  Molybdate  Solution 
20  grams  molybdic  oxide  dissolved  in  29  c.c.  strongest  ammonium 
hydroxide  and  54  c.c.  water.      Pour  slowly  and  with  stirring  into  98  c.c. 
strongest  nitric  acid  diluted  with  230  c.c.  water. 

Phenolphthalein  Solution  for  Indicator 
Dissolve  1  gram  of  phenolphthalein  in  100  c.c.  of  95%  alcohol. 


Apparatus  Needed  for  the  Experiments. 


General 


1  Small  hot  air  oven. 
1  Box  scales  weighing  to  1  kilo- 
gram. 
1  Inexpensive  balance  weighing 

from  0.01  to  100  grams. 
1  Six  inch  porcelain  mortar  and 

pestle. 
1  Compound  microscope. 
1  Gallon  battery  jar. 
1  Six  inch  funnel. 
12  One  liter  and  two  liter  wide 

mouthed  bottles,  or 
12  One  pint  and  one  quart  mason 

jars. 
12  One    pint    to    two    quart    tin 
dishes. 
1  Medium  sized  grater. 

Cheese  cloth. 
3  iron  crucibles,  50  c.c. 
Several  tin  covers  to  serve  as 
dishes  for  drying,  etc. 
1  1000  c.c.  cylinder. 
Assorted  rubber  stoppers  (so- 
lid) and  corks. 
1  Set  cork  borers. 
Small  magnifying  glass. 
Magnet. 


Pneumatic  trough. 

Blast  lamp  and  bellows. 

Files,  triangular  and  round. 

Wing  top. 

Assorted  rubber  tubing. 

Thistle  tubes. 

Blowpipes. 

Each  Student 

1  Bunsen  burner  and  tubing 
25  11  cm.  filter  papers. 

2  Porcelain  dishes,  3  inch. 

4  300  c.c.  and  2  50  c.c.  beakers. 
12  Test  tubes,  6  x  ^  inch. 
1  Crucible  tongs,  9  inch. 
1  Test  tube  clamp. 

1  Ring  stand  and  rings. 

2  Florence  flasks,  500  c.c. 
1  Wire  gauze,  four  inch. 

1  Burette  clamp. 
1  Cylinder,  100  c.c.  (graduated). 
1  Glass  funnel,  2  }/2  inch  diameter. 
1  Porcelain  crucible,  1^  in.diam. 

1  Hard  glass  test  tube,  8  in. 

2  Wide  mouth  bottles,  250  c.c. 
1  Watch  glass,  3  in.  diam. 

1  Test  tube  brush. 


INDEX 


(References  are  to  pages.) 


Acetic  acid,  128 

Acetylene,  124 

Acids,  80 

Acid  and  base  balance,  329 

Acid  phosphate  fertilizers,  110 

Agate,  135 

Alcohols,  126 

Aldehydes,  128 

Alfalfa,  187 

Alkali  metals,  141 

Alkaloids,  133,  137,  175 

Alloys,  158,  161 

Allotropism,  53 

Aluminium — 

Compounds  of,  165 

Hydroxide  of,  165 

Occurrence  of,  164 

Oxide  of,  165 

Preparation  of,  164 

Properties  of,  165 

Uses,  of,  165 
Alum,  165 
Amalgam,  161 
Amethyst,  135 
Ammonia — 

Chemical  properties  of,  84 

Composition  of,  84 

Distribution  of,  82 

In  the  atmosphere,  73 

Physical  properties  of,  84 

Preparation  of,  82 
Ammonium  sulphate,  216 
Analysis,  58 
Animal  Charcoal,  115 
Animals — 

By-products  of,  269 

Composition  of,  255 

Efficiency  of,  269 


Fuel  needs  of,  286 

Nutrition  of,  258 

Parts  of  body,  252 
Anion,  141 
Anode,  141 
Apatite,  199,  207 
Aqua  regia,  86,  94 
Argol,  129 
Argon,  74 
Artificial  silk,  340 
Asbestos,  159 
Ash,  176 

Ash  constituents,  285 
Assimilation,  265 
Atomic  theory,  61 
Atomic  weights,  61 
Atoms,  61 
Atmosphere — 

A  mixture,  75 

Composition  of,  67 

Definition  of,  167 

Weight  of,  67 
Atmospheric  dust,  74 

Babcock  test,  310 

Bacteria,  187 

Baking,  324 

Baking  powders,  324 

Baking  soda,  147 

Bases,  81 

Beans,  187 

Beet,  188 

Benzine,  124 

Beverages,  327 

Biochemistry,  177 

Bleaching,  43,  346 

Bleaching  powder,  92,  95,  154,  360 

Blood,  254 


425 


426 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Bluestone,  159 
Blue  vitrol,  159 
Boneblack,  118 
Bone  phosphate,  220 
Borax,  148 

Bordeaux  mixture,  359 
Brass,  158 
Bread,  319 
Bronze,  158 
Butter,  307 
Buttermilk,  307,  310 
Butyric  acid,  129 

Caffein,  133,  328 
Calcite,  200 
Calcium — 

Arsenite  of,  355 

Carbonate  of,  151,  154 

Compounds  of,  152 

Cyanamide  of,  217 

Distribution  of,  151 

Hydroxide  of,  154 

Hypochlorite  of,  95,  360 

Nitrate  of,  218 

Oxide  of,  152 

Pentasulphide,  356 

Phosphate  of,  151 

Preparation  of,  152 

Properties  of,  152 

Silicate  of,  151 

Sulphate  of,  151 
Calorimeter,  276 
Cane  Sugar,  131 
Canning  industry,  332 
Caramel,  131 
Carbides,  118 
Carbohydrates,  130,  317 
Carbolic  acid,  360 
Carbon — 

Amorphous,  114 

Bisulphide  of,  358 

Chemical  properties  of,  116 


Compounds  with  oxygen,  118 

Cycle  of,  122 

Dioxide  of,  71,  119 

Distribution  of.  111 

Disulphide  of,  100 

Monoxide  of,  118 

Organic  compounds  of,  122 

Properties  of,  110 

Uses  of,  118 
Carbon  dioxide,  71,  119 
Carborundum,  135 
Camahte,  223 
Castner  process,  143 
Casein,  299 
Cathode,  141 
Cation,  141 
Caustic  soda,  143 
Cells,  177 
Celluloid,  133 
Cellulose,  132 
Cement,  154,  349 
Centrifugal  method,  306 
Cereal  crops,  229,  320 
Chalk,  151,  155 
Charcoal,  115 
Cheese,  308 
Chemical  changes,  18 
Chemical  pieservatives,  334 
Chemical  properties,  19 
Chemistry — 

Definition,  11 

Importance,  13 

Relation  to  agriculture,  14 

Relation  to  physics,  18 
Chloride  of  lime,  92 
Chlorides,  94 
Chlorine — 

Action  on  water,  37 

Chemical  properties  of,  90 

Description  of,  89 

Distribution  of,  89 

Preparation  of,  89 


INDEX 


427 


Physical  properties  of,  90 
Chlorine  water,  92 
Chlorophyll,  183 
Chocolate,  328 
ChoKe  damp,  111 
Churning,  307 
Ciders,  322 
Citric  acid,  129 
Clay,  164 
Cleaning,  345 
Clover,  187 
Coal,  77,  113 
Coal  tar,  116 
Cocaine,  133 
Cocoa,  320,  328 
Coffee,  133,  327 
Coke,  115,  118 
Collodion,  132 
Colostrum,  299,  301 
Composition  of  animals,  255 
Composition  of  the  earth,  17 
Compounds,  14 
Concrete,  154,  351 
Conglutin,  175 
Conservation     of     matter     and 

energy,  13 
Cooking,  323 
Copper — 

As  fungicide,  358 

Chemical  properties  of,  158 

Distribution  of,  157 

Preparation  of,  157 

Physical  properties  of,  157 

Sulphate  of,  159 
Coral,  155 
Com,  188 
Com  syrup,  131 
Corrosive  sublimate,  860 
Cotton,  132,  338 
Cream,  304 
Crops,  187,  229 


Dairy  Products — 
Composition  of,  310 
Importance  of,  310 

Deflagration,  49 

Denitrification,  68,  78 

Dew  point,  70 

Dextrin,  132 

Dextrose,  131,  171 

Diamond,  112 

Diet- 
Balancing  the,  328 
Economy  in  cost  of,  331 

Dietetics,  314 

Differences  in  food  requirements, 
283 

Diffusion,  55 

Digestion,  258 

Disinfectants,  92,  360 

Dolomite,  200 

Dried  blood,  220,  271    • 

Dry  farming,  41 

Dyeing,  43,  344 

Dyeing  industry,  342 

Dyes — 

Analine,  343 
Coal  tar,  343 
Fastness  of,  344 

Efficiency  of  animals,  269 
Eggs,  319 

Electrolysis,  34,  141 
Electrolytes,  141 
Elements,  14,  16 
Emulsion,  298 
Energy,  12 
Enzymes,  127,  179 
Epsom  salts,  160 
Equations,  62 
Erosin,  39 
Esters,  129 
Ethers,  130 
Ethyl  alcohol,  127 


428 


Chemistry  of  the  farm  and  home 


Ethyl  ether,  130 
Environment,  190 
Excretion,  266 

Faxm  manure — 

Absorbents    and    preservatives 
of,  245 

Amount  of,  237 

Effects  of,  248 

Fertilizing  importance  of,  235 

Increasing  the  value  of,  246 

Losses  in  stored,  243 

Of  different  animals,  241 

Source  of,  236 

Use  of,  247 

Value  of,  239 
Fat  globules.  Relation  of  to  rate 

of  creaming,  305 
Fats,  129,  173,  317 
Feeding  of  animals,  274 
Feeding  standards,  290 
Feeding  stuffs — 

Building  and  fuel  values  of,  276 

Condimental,  291 

Influence  of,  302 

Laws,  292 

Manurial  value,  240 

Measure  of  digestibility  of,  267 

Nature  and  composition  of,  274 

Productive  value  of,  280 
Feldspar,  137,  164,  198,  207 
Ferro-sihcon,  135 
Fertilizers — 

Choice  of,  228 

Classes  of,  214 

Commercial,  214 

Complete,  224 

Containing    organic    nitrogen, 
219 

Home  mixing,  227 

Inspection  of,  225 

-Methods  of  application  of,  228 


Relative   availability   of   phos- 
phate, 223 

Retention  of  by  soils  minerals, 
209 

Superphosphates,  221 

Terms,  225 

Used  for  their  phosphorus,  220 

Used  for  their  potassium,  223 

Values  of,  226 
Fibrin,  299 
Filter- 
Charcoal,  28 

Sand,  28 
Fire  damp,  111 
Fish,  319 

Flavors  of  butter  and  cheese,  311 
Flax,  340 
Flint,  135 
Flux,  148 
Food- 
Absorption  of  digested,  263 

Acid-forming,  329 

Base-forming,  329 

Classes  of,  318 

Human,  314 

Influence  of,  291 

Preservation  of,  332 
Food  labels,  335 
Formaldehyde,  128,  360 
Formalin,  128 
Formulas,  62 
Fructose,  132 
Fruits,  321 
Fruit  sugar,  132 
Fuel  needs  of  human  body,  315 
Fungicides,  105,  358 

Garden  crops,  230 
Gasoline,  125 
Gases — 

Illuminating,  77 

In  milk,  303 


INDEX 


42d 


Solubility  of,  33 
Gelatine,  272 
German  silver,  158 
Glauber's  salt,  145 
Gliadin,  175,  320 
Globulin,  175 
Glucose,  131 
Glue,  272 
Glutin,  320 
Glycerine,  128 
Granite,  137 
Grape  sugar,  131 
Graphite,  111,  113. 
Grass  crops,  230 
Green  manuring,  249 
Guncotton,  132 
Gunpowder,  49 
Gypsum,  151,  210,  228 

Halogens,  95 
Hard  waters,  156 
Hart  test,  310 
Harvesting,  188 
Helium,  74 
Hemp,  341 
Hexoses,  171 
Humus,  197,  201 
Hydrocarbons,  123 
Hydrochloric  acid — 

Chemical  properties  of,  94 

Physical  properties  of,  93 
Hydrocyanic  acid,  357 
Hydrogen — 

Character  of,  53 

Chemical  properties  of,  56 

Distribution  of,  53 

Peroxide  of,  57,  361 

Physical  properties  of,  55 

Preparation  of,  53 

Sulphide  of,  99 

Usefulness  of,  56 
Hydrogen  peroxide — 


Preparation  of,  57 

Properties  of,  57 

Uses  of,  57 
Hydrolysis,  263 
Hypothesis,  12 

Iceland  spar,  155 
Illuminating  gas,  77 
Ink,  346 
Insecticides,  353 
Ion,  141 
Iron — 

Distribution  of,  162 

Kinds  of,  163 

Preparation  of,  162 

Properties  of,  163 

Uses  of,  163 
Irrigation,  42,  210 

Kainite,  223 
KaoUn,  137 
KaoUnite,  198 
Kerosene,  125 
Kidneys,  267 
Kieselguhr,  133 
Kieserite,  223 
Kindling  temperature,  49 

Lactalbumin,  299 

Lactation,  influence  of,  301 

Lactic  acid,  129 

Lactose,  131 

Lampblack,  114 

Laughing  gas,  87 

Law,  A,  12 

Law  of  definite  proportions,  46 

Lead  arsenate,  355 

Lead  carbonate,  347 

Leblanc  process,  146 

Legumes,  77,  187,  229,  319 

Levulose,  132,  171 

Lignification,  178 


430 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Lignite,  113 
Lime-kiln,  152 
Lime  light,  153 
Limestone,  151,  228 
Lime-sulphur,  355 
Limewater,  154 
Limonite,  200 
Linen,  132,  340 
Liquid  air,  76 
Lye,  143 

Macaroni,  320 
Magnesium — 

Carbonate  of,  160 

Compounds  of,  160 

Distribution  of,  159 

Oxide  of,  160 

Preparation  of,  159 

Properties  of,  160 

Sulphate  of,  160 

Uses  of,  160 
Malic  acid,  129 
Malt.  127 
Maltose,  131,  171 
Malt  sugar,  131 
Manures.     See  Farm  Manure 
Manurial  value  of  feeding  stuffs, 

240 
Maple  sugar,  131 
Marble,  151,  155 
Marl,  155 
Marsh  gas,  123 
Matches,  109 
Matter,  12 
Meats,  319 
Meerchaum,  159 
Mercury  bichloride,  360 
Metallurgy,  140 
Metals — 

Extraction  of,  140 

Occurrence  of,  140 
Methane,  123 


Methyl  alcohol,  126 

Mica,  137,  164 

Micro-organisms,  75 

Milk- 
Chemical  composition  of,  297 
Condensed,  304 
Decomposition  of,  303 
Food  value  of,  318 
Gases  of,  303 
Mothers'  284 
Of  different  animals,  300 
Of  different  breeds,  300 
Specific  gravity  of,  296 

Milk  of  Ume,  154 

Milk  sugar,  131 

Mineral,  140 

Mineral  phosphates,  221 

Mixtures,  16 

Molds,  309 

Molecules,  61 

Monocalcium  phosphate,  222 

Morphine,  77,  133 

Mortar,  349,  352 

Muriate  of  potash,  224 

Myristin,  298 

Necrosis,  107 
Nerves,  255 
Nicotine,  133 
Nitric  acid — 

Chemical  properties  of,  85 

Preparation  of,  85 

Physical  properties  of,  85 

Usefulness  of,  86 
Nitre,  150 
Nitrides,  79 
Nitrogen — 

Chemical  properties  of,  79 

Component  of  atmosphere,  68 

Compounds  of,  80 

Cycle  of,  77 

Description  of,  76 


INDEX 


431 


Distribution  of,  76 

Oxides  of,  86 

Peroxide  of,  87 

Physical  properties  of,  79 

Preparation  of,  78 
Nitroglycerine,  128 
Nucleo-proteins,  174 
Nutrition  of  the  animal,  258 
Nutritive  ration,  281 
Nuts,  319 

Occlusion,  55 
Oiis,  129,  174 
Olein,  130,  298 
Oleomargarine,  308 
Onyx,  135,  155 
Opal,  135 
Opium,  133 
Orchard  crops,  230 
Ore,  140 

Organic  acids,  128 
Organic  chemistry,  122 
Orthoclase,  148 
Osmosis,  181 
Overrun,  308 
Oxalic  acid,  129 
Oxidation,  48 
Oxygen — 

Chemical  properties  of,  47 

Component  of  air,  68 

Evolution  of,  46 

Physical  properties  of,  46 

Storage  of,  51 

Testing  of,  48 

Uses  of,  50 
Ozone — 

Preparation  of,  52 

Properties  of,  52 

Relation  of  oxygen  to,  52 

Paints,  347 
Palmitin,  130,  298 


Paper,  132 
Paris  green,  354 
Pasteurizing,  307 
Pearls,  155 
Peas,  187 
Peat,  113 

Petroleum,  111,  124 
Petroleum  oils,  357 
Phosphoric  acid,  222 
Phosphorus — 

Chemical  properties  of,  107 

Compounds  of,  108 

Description  of,  105 

Distribution  of,  106 

Physical  properties  of,  107 

Preparation  of,  106 

Red,  108 

Uses  of,  109 
Physical  properties,  19 
Pitch,  175 
Plant- 
Chemical  changes  of,  178 

Composition  of,  169 

Dry  matter  of,  170 

Flower  and  fruit  of,  185 

Growth  of,  176 

Importance,  of,  168 

Leaf  of,  183 

Nutrition  of,  185 

Organic  compounds  of,  170 

Stem  of,  182 

Structure  of  cell,  177 
Plasmolysis,  178 
Plaster,  352 
Plumbago,  113 
Polysilic  acids,  136 
Porcelain,  166 
Potassium — 

Chemical  properties  of,  149 

Chloride  of,  224 

Compounds  of,  149 

Distribution  of,  148 


432 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Hydroxide  of,  149 

Nitrate  of,  150 

Physical  properties  of,  149 

Preparation  of,  149 

Uses  of,  150 
Products  of  farm  animals,  268 
Protein  needs  of  animals,  288 
Protein  needs  of  human  body,  316 
Proteins,  174,  288,  298,  316 
Ptomaines,  332 
Pulverizing  agents,  202 
Pure  food  laws,  335 
Pyroligneous  acid,  128 
Pyroxylin,  132 

Quartz,  135,  197 
Quicklime,  151,  152 
Quinine,  77,  133 

Rain  water,  25 

Rancidity,  307 

Reduction,  56 

Respiration,  265 

River  water,  25 

Rocks   and   Plants,    Relation   to 

soil,  195 
Root  Crops,  188,  230 
Rotation  of  crops,  190 
Roughage,  Value  of  indigestible, 

219 
Rubber,  175 
Rusting,  38 

Safety  lamp,  50 
Safety  matches,  109 
Salaratus,  147 
Sal  soda,  145 
Salt,  144,  332 
Salt  lakes,  26 
Saltpetre,  76,  150 
Salts,  81 
Sand  culturej  18^ 


Sandstone,  137 
San  Jose  scale,  355 
Saturation,  70 
Sea  water,  26 
Selenite,  199,  207 
Separator,  306 
Sewage,  249 
Shells,  151,  155 
Silage,  188 
Silicic  acids,  136 
Silicides,  134 
Silicon — 

Compounds  of,  134 

Dioxide  of,  134 

Distribution  of,  133 

Preparation  of,  134 

Properties  of,  134 
Silk,  342 
Skin,  The,  266 
Slag,  162,  221 
Slaking,  153 
Soap,  130 
Soapstone,  159 
Sodium — 

Bicarbonate  of,  147 

Carbonate  of,  145 

Chemical  properties  of,  142 

Chloride  of,  89,  144 

Compounds  of,  143 

Distribution  of,  142 

Hydroxide  of,  143 

Hypos  ulphate  of,  145 

Nitrate  of,  147,  215 

Physical  properties  of,  142 

Preparation  of,  142 

Sulphate  of,  145 

Tetraborate  of,  148 

Thiosulphate  of,  145 
Soil— 

Alkah,  210 

Analysis  of,  211 

Chemical  properties  of,  207 


INDEX 


433 


Heat-absorbing  power  of,  206 

Minerals  of  the,  196 

Nitrification  of,  208 

Nitrogen  from  air,  217 

Origin  of,  193 

Physical  properties  of,  205 

Soil  amendment,  227 

Texture  of,  204 

Water  of  the,  25 
Soil  water,  25 
Solubility,  32 
Solvay  process,  146 
Spices,  326 

Spontaneous  combustion,  49 
Spot  cleaning,  345 
Spring  water,  25 
Stains,  346 
Stalactites,  155 
Stalagmites,  155 
Starch,  132,  172,  319 
Stassfurt  salts,  223 
Stearin,  130 
Steel,  163 
Stoneware,  166 
Strawberry,  188 
Sucrose,  131,  171 
Sugar,  131,  332 
Sulphates,  105 
Sulphur — 

Chemical  properties  of,  98 

Compounds  of,  99 

Dioxide  of,  101 

Distribution  of,  96 

Oxide  of,  101,  102 

Physical  properties  of,  97 

Preparation  of,  96 

Trioxide  of,  103 

Uses  of,  98,  358 
Sulphuric  acid — 

Properties  of,  104 

Uses  of,  105 
Sulphuric  ether,  130 


Sulphur  trioxide,  103 

Sylvanite,  223 

Symbols,  62 

Synthesis,  58 

Systems  of  fertilization,  231 

Talc,  159,  198 
Tankage,  271 
Tannin,  271 
Tanning,  269 
Tartaric  acid,  129 
Tea,  133,  327 
Terpenes,  175 
Theory,  12 
Theine,  133 
Toasting,  325 
Tobacco,  133 
Turnip,  188 
Turpentine,  175 

Udder,  The,  295 
Urine,  241 

Varnishes,  347 
Vegetables,  Cooking  of,  325 
Verdigris,  158 
Vinegar,  128,  322 
Vitriosil,  136 
Vitriol,  Oil  of,  105 

Washing  soda,  145 
Water — 

Action  of  chlorine  on,  37 

Action  of  metals  on,  37 

Amount  of  in  certain  products, 
23 

As  a  chemical  agent,  37 

As  a  solvent,  31 

Chemical  properties  of,  33 

Circulation  of,  26 

Climatic  effects  of,  40 

Distribution  of,  22 


434 


CHEMISTRY  OF  THE  FARM  AND  HOME 


Importance  of,  22 
In  the  soil,  25 
Kinds  of,  24 

Physical  properties  of,  30,  46 
Purification  of,  27 
Relation  to  plant  life,  41 
Relation  to  the  soil,  41 
Usefulness  in  nature,  39 
Vapor  of,  69 

Water  culture,  186 

Water  vapor,  69 

Waxes,  175 

Whiting,  156 

Wilting,  178 

Wines,  322 

Wood  ashes.  224 


Wool,  341 

Workingmen's  food  requirements, 
317 

Zein,  175 
Zeolites,  210 
Zinc — 

Arsenite  of,  355 

Chemical  properties  of,  161 

Chloride  of,  161 

Compounds  of,  161 

Distribution  of,  160 

Oxide  of,  161 

Physical  properties  of,  161 

Preparation  of,  160 

Uses  of,  161 


Agricultural  Text  Books 

FOR 

HIGH  SCHOOLS 

Published  by 

WEBB  PUBLISHING  CO..  ST.  PAUL,  MINN. 


This  series  of  agricultural  books,  of  which  Agricultural  Engineering 
is  a  representative,  is  planned  especially  for  high  schools  in  which 
agriculture  is  taught.  The  books  constitute  a  complete  four-year 
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will  meet  the  urgent  needs  of  the  modern  agricultural  high  schools  and 
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FIELD  CROPS 


By  A.  D.  WILSON,  Sup't  of  Farmers'  Institutes  and  Exten- 
sion, Minnesota  College  of  Agriculture,  and  C.  W. 
WARBURTON,  Agronomist,  U.  S.  Dep't 
of  Agriculture. 


544  pages,  162  illustrations,  cloth,  $1.50  net. 


The  aim  of  this  book  is  to  present  the  peculiarities  of  each  of  the 
various  classes  and  varieties  of  farm  crops,  the  handhng  of  the  soil, 
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discuss  the  theory  and  practice  of  crop  rotation  and  weeds  and  their 
eradication.  A  list  of  the  best  supplementary  reading,  including 
farmers'  bulletins,  is  given  at  the  close  of  each  chapter.  The  style  is 
easy,  subject  matter  well  arranged  and  vital,  and  the  book  is  of  excel- 
lent mechanical  makeup  throughout. 


STANDARD  AGRICULTURAL  BOOKS 

BEGINNINGS  IN  ANIMAL 
HUSBANDRY 

By   CHARLES   S.    PLUMB,   Professor   of  Animal  Husbandry,   College 
of  Agriculture,   Ohio   State   University. 

395  pages,  217  illustrations,  cloth,  $1.25  net. 

Beginnings  in  Animal  Husbandry  is  a  book  that  will  be  found  to 
be  of  interest  and  invaluable  assistance  to  the  farmer.  Among  the  sub- 
jects discussed  are:  The  Importance  of  Animal  Husbandry;  Breeds 
of  Horses,  Cattle,  Sheep  and  Swine;  Animal  Type  and  Its  Importance; 
Reasons  and  Methods  in  Judging  Live  Stock;  Points  of  the  Horse; 
Judging  Horses,  Cattle,  Sheep  and  Swine,  etc.;  Heredity:  Its  Meaning 
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Types  and  Breeds,  Judging,  Feeding;  Eggs  and  Incubation;  Poultry 
Houses.     Every  subject  discussed   fully. 


SOILS  AND  SOIL  FERTILITY 

By  A.  R.  WHITSON,  Professor  of  Soils  and  Drainage,  and  H.  L. 
WALSTER,   Instructor  of  Soils,   Univ.   of  Wis. 

315  pages,  well  illustrated,  cloth,  $1.25  net. 

No  other  book  on  Soils  presents  the  relation  of  the  soil  to  the 
production  of  crops  in  so  clear  and  agreeable  a  manner  as  this.  There 
are  chapters  on  the  following:  Conditions  Essential  to  Plant  Growth, 
Origin  and  Classification  of  Soils;  Primary  Relations  of  Soil  and  Plant; 
Nitrogen;  Phosphorus  and  Potash;  Soil  Analysis;  Farm  Manure;  Com- 
mercial Fertilizers;  Physical  Properties  of  Soils;  Water  Supply;  Tem- 
perature and  Ventilation  of  Soils;  Drainage;  Erosion;  Tillage;  Humus; 
Relation  of  Crops  to  Climate  and  Soil;  Soils  of  the  United  States; 
Management  of  Important  Types  of  Soil;  Dry  Farming.  Explicit 
language  and  the  avoidance  of  technical  matter  make  the  book  ideal 
for  those  interested  in  a  practical  study  of  soils. 


DAIRY  LABORATORY  GUIDE 

By  G.  L.  MARTIN,  Professor  of  Dairying,  North  Dakota  Agricultural 

College. 


140  pages,  illustrated,  cloth,  50c  postpaid. 

This  laboratory  manual  offers  a  carefully  organized  series  of  exer- 
cises covering  the  principles  of  modern  dairy  practice,  with  sugges- 
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Testing,  Manufacturing,  and  Marketing,  of  Dairy  Products.  An  indis- 
pensable guide  for  classes  in  Dairying  and  for  Creamerymen. 

STANDARD  AGRICULTURAL  BOOKS 


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